About "git rebase"

[Benoît Minisini <benoit.minisini@xxxxxxxxxxxxxxxx>]

Hi,

I have a question about git: I have a friend I work with that uses "git 
rebase" sometimes, and half the time it breaks the contents of its local 
repository, and then the share git repository when it pushes its commits.

Does anyone use "git rebase"? If so, can he explain what the purpose of 
this command is exactly? I have never used it myself.

Thanks in advance!

--
Benoît Minisini.