What is the difference between Bukkit and CraftBukkit?

All around the web, I usually read "Are you using Bukkit or CraftBukkit?".
I use this jar to develop using the API but now I see there is a tab named "Bukkit", too.
So what is the difference between these two downloads? Which should I use?

 

Joiner
Bukkit is the jar developers are supposed to build on to create plugins, letting them use the API. CraftBukkit is what servers run on, letting server owners use it to actually make a server. Developers can use either jar to develop though, however, CraftBukkit can let you use NMS code and other trickery's to let you actually change how the server runs.

 

Googlelover1234 How is it possible that Bukkit is 5MB and CraftBukkit is 20MB?

 

Probably because craftbukkit is used to run the server so is larger.

 

Joiner
This has been answered ridiculous amounts of times already. Please learn to search...

 

Joiner
Yes, like what 17xDillz1997 said, the Bukkit.jar = ONLY API. The API just gives you what you need to develop plugins. CraftBukkit.jar = API + SERVER. The server is a lot larger than the API.

 

Googlelover1234
Does CraftBukkit.jar have an API? I thought it just contained the server files which are obfuscated. If it does have an API, what's the point of Bukkit.jar?

 

EgyptianKing Its obfuscated but useful.

 

Moved to Bukkit Discussion.

Locked since there are already way too many Threads about this. It is also already answered in the FAQ:
http://wiki.bukkit.org/FAQ#What_is_the_difference_between_Bukkit_and_CraftBukkit.3F