The thing about expansion in eve is while they do effect everyone being it's one server, sometimes the content won't really reach you.
However don't worry there are lots of updates in every expansion to fix bugs or balance gameplay, add items and such. New ships, new weapons.
However that real expansion part that introduces new gameplay doesn't always effect you directly.
by expansion
castor
tech level 2
Tech Level 2 has been introduced, bringing exciting new manufacturing and research possibilities into the world of EVE.
player owned conqureable stations
With the introduction of player owned stations in deep space, Alliances could vie for control of the outer regions.
new ship classes
Tech Level 2 versions of current ship classes called Elites started to make their appearance.
new agent features
Agent feature has been revamped, making it easier than before to get new and better quality agents and missions that bring greater rewards.
market changes
Market changes include: enhanced interface and options, more accurate order prices, NPC price fluctuations to reflect supply and demand fluctuations and much more.
updated ship technology
Engineering breakthroughs enhance ship technology with increased mass and/or available module slots have been implemented, along with increased cargo capacity, capacitor recharging rates and much more.
crime fighting
Bigger risk and more rewarding in an answer to the deployment of cruisers and battleships by underworld figureheads.
advanced skills
SoCT offer continuing education opportunities that will enhance scholars' knowledge in subjects such as ore refining, weapon upgrades and drone management
weapon upgrades
Turret changes affect combat with missile enhancements, controlled splash damage, projectile and hybrids getting a boost.
auto-cloak
Auto-cloaking protects stargate patrons by temporarily enveloping ships in a shimmery camouflage field, obscuring them from view.
Expansion 2
Exodus
new ships
Destroyers, Battlecruisers, Faction ships and Mining barges!
starbases
With the introduction of player owned Starbases, EVE will become a game of territorial conquest.
new helper applications
Calculator and notepad will be appearing in a taskbar near you.
new multi-level scenarios
These are massive multi-levelled space game arenas called Complexes commonly known as dungeons.
system scanning
Safespots beware! They are no longer ... safe! You could also find other hidden things such as Complexes or Comets.
mining improvements
Improvements to mining and new Ice field environments to harvest.
corporation improvements
Corporations are as difficult to manage in EVE as in real life. These improvements should allow for better control of corporation assets.
alliance systems
Alliances are a major part of EVE and with this system, all players of an alliance will be able to fly under the same flag.
war declaration
New War Declaration and rules with better handling of conflict and war.
user interface improvement
There will be a plethora of UI improvements to accommodate for new features and to lessen the learning curve for new players.
new agent functionality
With new these enhancements the Agent system will leap forward and become an important part of the game.
new aggression system
Extended criminal and contraband flagging.
new npc types
Over 200 new NPCs will be added including NPC Commanders and Officers that carry ultra-rare loot and very high bounties, mining operations and rogue drones
market improvements
Market accessible from space and new functionality.
fleet command and tactical view
Wing hierarchies and setting of objectives.
updated ingame browser
Updated Ingame Browser with HTML 3.2 support and EVE specific tags.
Expansion 3
Cold war (to much text going to only include BIG changes)
cosmos constellations
Outposts
system sovereignty
dreadnuats
freighters
lots of other stuff
Expansion 4
Red Moon Rising
-Titans
-Motherships and carriers
-23 new Tech 2 ships
-tech 2 ammo
-Fighters
-New bloodlines
-Project rebrith (jump clones! OMG)
-eye for an eye
-tractor beams!
-Elite evil NPCs added
-other stuff
Expansion 5
Revalations
-Contracts (players can make ebay type stuff and missions for players to move things or kill people for isk)
-Exporation \o/
-combat boosters (drugs!)
-new battleships
-Salavging
-InGame voice comuncation (before anyone else did it)
-rigs
-Invention
-New battlecruisers
-Fleet system
-otherstuff
Expansion 6
Revalations 2
-the small expansion
-overheating
-bombs
-Sov system
-tons of tons of improvments but not expansion stuff really
Expansion 7
Trinity
-SHINY
-MORE SHINY
-female corpses :P
-lots of other stuff like ships and stuff but you cares shiny:)
Expansion 8
Factional warfare \o?
-another "small" expansion
Factional Militias
Governments on every side of the war are eager to recruit pod pilots, and have set up factional militias as a means of bolstering their standing navies. Each faction has a corporation open to all pilots with the appropriate factional standing minimums. CEOs and directors are also encouraged to bring their entire corporations under the aegis of the militias, to better fund and coordinate the war effort. Regardless of corporation membership, all militia members will share a chat channel and read-only mailing list.
Ranks
Each of the factions relies heavily upon the support of their militias, granting the privateers great political clout. Talented pilots dedicated to the cause can rise through the newly-created ranks, 10 for each faction, by increasing their standing with their chosen militia's corporation.
Factional Warfare Agents
In order to handle the influx of mercenary pilots, each of the four militia corporations have hired new agents-over 320 in all. These new agents are specifically tasked with coordinating the activities of freelance pod pilots and assigning them missions inside territory held by enemy militias.
Statistics
Due to the emphasis placed on the role of militias in the conflict, many stations now boast new Militia Offices. Pilots can track their own warfare victories and kill statistics, as well as those of their corporation and faction. Each pilot's map has also been upgraded to better accommodate the increased flow of logistics data. The galactic map can now be configured to show occupancy status of a system, as well as detecting the presence of hostile navy forces.
System Occupancy
In light of the formal declaration of war, CONCORD is now recognizing a new level of system control beyond sovereignty: occupancy. Factions gain occupancy of a system by winning conflicts in contested complexes. When a militia accumulates a certain number of victories for its faction, it is authorized to assault the star's System Control Bunker within 24 hours. Should the bunker fall to the attacking militia, a cease-fire is called in the system's Factional Warfare Complexes, and that faction gains occupancy of the solar system.
Combat Zones
As the fighting has spread throughout the inhabited regions of space, many of them have been deemed Combat Zones. Most of these contested regions are located in low-security space, but not all. Regardless of their security level, each of the systems within a Combat Zone contains a System Control Bunker near their stars. These bunkers coordinate all activity within their system's Factional Warfare Complexes.
Factional Warfare Complexes
As war rages across the stars of New Eden, a myriad of hidden deadspace complexes have taken on great strategic importance. Militia pilots that successfully scan for a complex and hold it uncontested for a set amount of time will claim it for their faction, and be rewarded with corporate standing-as well as more tangible benefits. But capturing these points of interest will not be easy, as they're guarded by rival naval forces. Speed and cunning are required to keep these important sites out of enemy hands, which is why microwarpdrives have been cleared for use in the complexes.
World Shaping
The confines of settled space cannot contain a war of this scale, causing the fighting to spill over into a new region. Named "Black Rise," this new region contains 49 new star systems and nearly 40 stations, many of which are already sworn to one faction or another.
So for the most part you'll find the winter expansion is HUGE while the summer expansions are "small"
plus between each expansion are 2 HUGE patches which add content as well, sometimes ships, or new missions, bug fixes or new graphics, but nothing that expands the game just makes it bigger.
However the next expansion may also be "small" as ambulation will apartnely need 6 more months before release.
