Invoking the magit-status function will show a buffer with the
status of the current git repository and its working tree.  That
buffer offers key bindings for manipulating the status in simple
ways.

The status buffer mainly shows the difference between the working
tree and the index, and the difference between the index and the
current HEAD.  You can add individual hunks from the working tree
to the index, and you can commit the index.

See the Magit User Manual for more information.