Cloning a repository puts a copy of your code on the computer you clone it to.
Adding a file prepares the file for a commit. Files in Github desktop with changes are automatically added (checkbox).
Committing code means updating your local version of the repository to the latest version.
Pushing code updates your remote version of the repository i.e. the repository on github.swarthmore.edu.
Pulling code updates your local version of the repository from your remote version of the repository.