SSH stands for Secure Shell.
When working with a GitHub repository,
you'll often need to introduce yourself to
GitHub using your username and password.
SSH key is an alternate way to identify yourself
that doesn't require you to enter you username and password every time.
SSH keys come in pairs, a public key that
gets shared with services like GitHub,
and a private key that is stored only on
your computer. If the keys match, you're granted access.