I also posted this on Se7ensins so don't go saying i copied and pasted it from there.
Zombie Modes
Treyarch revealed three modes during its preview event, detailing them in a presentation at the end of a day of multiplayer hands-on. One mode will be instantly recognizable to fans of other Treyarch Call of Duty games.
'Tranzit' adds scale to the original gametype, and acts as the primary mode for zombie players. Rather than be stuck in one location, players are free to explore a "big, giant, expansive world." Calling it "significantly bigger than anything [Treyarch has] ever created," Lamia promises players (playing solo or up to four-players co-op) can traverse on foot or via the bus featured in the zombies world premiere trailer above.

"Because it's open and because there are multiple locations in this world where you can play and where the infestation is, there's different strategies about how you can approach it," he adds. "It's a much bigger world with much more going on." Moving through the world in the bus has tactical advantages, such as speed; however, it isolates players and can become very difficult to escape from. Going it on foot "into the fog" which players can do by themselves or as part of the group also has its perks, but puts players in the middle of danger.
To aid in their survival, players can collection pieces of items from throughout the world, putting them together to create "buildables"; including weapons, tools and things to help open new areas of the world.
'Survival' has the "more classic zombies vibe," where zombie aggressors attack the player within a single area from the "expansive" Tranzit world. From its description, things work relatively the same as they have in the past: hole up, fortify your location and venture out to grab bonuses scattered throughout the environment when you find the right moment.

Survival areas are "carved out" of the Tranzit world and customized by Treyarch to act much like dedicated maps. Though Lamia wouldn't give an exact number, he promised players will have access to "multiple areas" in Survival that are designed to be played as a standalone section (solo or as a 4-player co-op experience). These areas feature the same gameplay zombie fans are used to, including magic items and 'Pack-a-Punch' machines.
'Grief' is a new mode, available for up to 8 players that takes the concept of Survival and adds a competitive twist. In this mode, two teams of four players are dropped within the zombie-infested Tranzit world and must outlive the opposing team.

"This is what I've called in the past '4z4,'" Lamia says, detailing a mode that breaks down to a simple descriptor of Humans vs. Humans vs. Zombies. "It's really humans versus zombies, because the zombies don't care what team you're on. They just want human flesh and brains."

In this mode, human players cannot kill each other; however, they can play with the world to put the opposing team in precarious situations hence the name 'Grief.' The last human team standing wins the match.

Standard elements like blocking passages seem to be on the docket to make the other team's life harder, but Lamia says there are "new mechanics exclusive to this mode" that players can employ to grief the other team with. When pressed for details, Lamia wouldn't budge on what those elements are.

How the Multiplayer Engine Changes Things
In Call of Duty: Black Ops 2, the zombies mode has been built on the multiplayer engine. In the past, Treyarch has stated this decision allows the developer to do new things it was unable to do in previous iterations. But what does that mean?
Stat tracking: Zombie fans will now have "extensive stats" attached to their monster hunting sessions, much like multiplayer fans have in the competitive part of the game.
Leaderboards: Stat tracking transitions into leaderboards for each zombie mode and can be broken down in detailed ways, like ranking based on maps. As an example, Lamia says players could check rankings for Survival in one particular area. "That will have its own leaderboard," Lamia added, mentioning detailed breakdowns for the other modes as well. "A lot more leaderboards, a lot more stats."
Improved Matchmaking: Using the multiplayer system, the game will attempt to match players faster than it has in the past. Because stats are tracked, Lamia says, Treyarch "will do [its] best" to match players with similar skill in the zombies mode. Of course, players can jump in and play with friends or anyone of varied skill levels if they choose.
Custom Games: "Now we're going to let you create custom games of the modes I just talked about," Lamia says. Creating a custom zombie game, players can make a series of decisions including setting a starting round (with players given points at the beginning of the match that are relative to the round choice, so players can purchase weapons and items to help them survive), you can set challenges like 'Headshots Only' at the beginning of the match or at specific rounds, turn magic items off (no perk machines, no 'Pack-a-Punch,' no mystery boxes). Lamia says there will be a laundry list of tweaks players can make.
Zombie Basics
A few additional details we were able to squeeze out of Treyarch regarding Zombies.
The mode features four new playable characters, including a female survivor teased in promotional art for the game.
Because the mode has no established narrative, Treyarch won't tell us what era the they envision the survivors living in. The single-player mode in Black Ops 2 shifts between the 1980s and the year 2025, while multiplayer takes place exclusively in the near-future setting. While some weapons in the teaser trailer point to a future timeline, Lamia tells us that its date remains a mystery as it's part of the narrative "fans are creating for the mode."
Zombies only exists because of fan feedback. Treyarch loves the mode, but only continues to grow it because of fan demand.
There are more zombie types, including new "normal zombies" and new "special zombie" adversaries.
There's a lot revolving around the zombie gametype and all modes, really that Treyarch won't be revealing. The developer wants to keep some surprises for players when the game launches.
Lamia promises plenty of Easter Eggs hidden throughout the Tranzit environment.
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Yes, This is a copy and paste from Joystiq but whatever.