Ganking is when a big group of players team up on one lone player, usually by surprise. Level differential is not necessary to be called ganking. In many games (mostly MMOs), this is a form of griefing, but in other games it is a legitimate and encouraged strategy.
For example, in DotA, ganking is an integral part to team victory. One player may roam around the map helping to ambush and team up on enemies who get caught out of position.
The two terms are orthogonal - an expansion pack might be DLC, but that would imply two different facts:
- It is downloadable, e.g. it can be obtained entirely via online means and installed automatically into the game.
- It adds significant features into the game.
DLC - "downloadable content" - is a very broad term for any additional parts of a game that you can obtain from any of the various online vendors. It's generally reserved for official content from the original publisher, to distinguish it from community content. That is, an additional module for Skyrim to add fancy armor for your horse would be a "mod" if a user did it, but "DLC" if Bethesda did it. DLC can also be very big; for Skyrim, both Dawnguard and Hearthfire are DLC and they make extensive changes to the game.
An "expansion pack" is a separate product that builds on top of an existing game to add significant new features. Expansion packs can usually be purchased at retail and installed from CD, and exist separately from their parent game. They are typically "mini games" in their own right, but rely on the content and engine of their original game for much of their content. In Skyrim, Dawnguard is obviously an "expansion pack" - it add new lands, new weapons, new skill trees, etc. I don't know if it's available for retail yet but I would be very surprised if there's not a Skyrim GOTY edition that includes the two expansion packs.
A better example might be Oblivion: there was a handful of DLC released, including horse armor and Knight of the Nine. Later, there was an actual expansion pack - Shivering Isles - that added an entire new land and new features into the game. (The line was blurried a bit when Bethesda packaged all of their DLC onto a CD for retail sale, but it was basically the same as downloading the DLC and burning the archives to to disk.)
With so much game delivery being online these days, and with official downloadable content getting bigger, the line between a "plug-in" and an "expansion pack" is blurring, and all of it would be considered "DLC".
Best Answer
Rubber banding is a term that's used to refer to a player's random or sporadic jerky movement during a multiplayer game if they're experiencing high latency. This happens more in certain games than others, but it is most noticeable in FPSs or similar games with a large number of people per multiplayer server. It is particularly prevalent in MMOs - the large number of players means there are more cases of rubber banding; either the server is overloaded or players have high ping. When rubber banding occurs, the player's character appears to rebound forwards and backwards very jerkily, as the server tries to calculate their position based on the high latency data they're transmitting. It is called rubber banding because it looks like the character is caught in a rubber band, being pulled and bounced forwards and backwards, appearing to be in one position one moment, then teleporting several metres away the next. The player's motion may also appear differently to different people - this explains why your friend saw himself rubber banding around on his screen, but to you he was motionless (which is common when looking at a lagging player).
Note that as Jeff mentioned, rubber banding in racing games refers to a type of AI that prevents them from getting too far ahead of the player.