The git commit
command does a few things:
blobs
and trees
to represent your project directory - stored in .git/objects
commit
object with your author information, commit message, and the root tree
from step 1 - also stored in .git/objects
HEAD
ref in .git/HEAD
to the hash of the newly-created commit
This results in a new snapshot of your project being added to git
that is connected to the previous state.