What are SSH keys for?

You create a pair of keys using ssh-keygen. These are plain text and can be cut and pasted , copied, as required. One is private (e.g. id_rsa), and you need to protect this as you would any other security artifact such as server passwords, and you can optionally
secure with a pass phrase. The other is public (e.g.id_rsa.pub), and you can share with anyone.