The checked out file will overwrite not yet commited changes you did in this file.

This command will check out the file file.example (which is located in the directory path/to/) and overwrite any changes you might have made to this file.

git checkout some-branch path/to/file

*some-branch can be anything tree-ish known to git (see Revision Selection and gitrevisions for more details)*

You have to add -- before the path if your file could be mistaken for a file (optional otherwise). No more options can be supplied after the --.

git checkout some-branch -- some-file

The second some-file is a file in this example.