To see your changes since the last commit:

$ git status

To commit the code of your local copy to your local repository:

# a single file
$ git commit path/to/this_file -m 'my commit message' 
# all files
$ git commit -am 'my commit message'

To push the code of your local copy to the master:

$ git push

To get the code from the master to your local copy:

$ git pull