what is fetch?

[Tim Crall]

Fetch downloads the specified content and puts it in a special commit pointed to by FETCH_HEAD but (unlike pull) does not attempt to merge it into the existing content.

[Arthur Hester]

http://stackoverflow.com/questions/292357/what-are-the-differences-between-git-pull-and-git-fetch 

GIT: FETCH AND MERGE, DON’T PULL 
http://longair.net/blog/2009/04/16/git-fetch-and-merge/