SSH keys are access credentials that are used in the SSH protocol.
Since it is highly likely that you will be using SSH connections on a daily basis, it is important that your connections would be secure.
These keys allow to authenticate SSH connections and offer strong encryption.
In certain scenarios, it could even be faster and more convenient to use SSH keys, especially when you are required to connect to many different servers regularly.
For more information on how to generate an SSH key pair, you might want to read the following article: https://kb.heficed.com/en/articles/2713461-how-to-generate-and-use-ssh-private-public-keys