Reverts all changes (from the last commit)
git checkout -- .
Reverts 
some.txt
 file changes from the last commit (to discard changes in working directory)
git checkout -- some.txt
HEAD will be detached and pointed towards the commit (to go back to master 
git checkout master
 should be run)
git checkout b4ba3088679ff70b45df2aefc7c0a13d41a2bd76
Reverts all changes (from the specified commit)
git checkout b4ba3088679ff70b45df2aefc7c0a13d41a2bd76 .
Reverts 
some.txt
 file changes (from the specified commit)
git checkout b4ba3088679ff70b45df2aefc7c0a13d41a2bd76 some.txt
To switch to an existing branch
git checkout another_branch
To switch to a new branch
git checkout -b new_branch