Setting up a public/private keyset for SSH allows you to log in to another machine running SSH without having to manually enter a password. This can be useful for saving time or automated processes. The setup consists of merely two simple steps.

Firstly at a terminal prompt, type:

ssh-keygen -t dsa

You will then see the following (or similar):

Generating public/private dsa key pair. Enter file in which to save the key (~/.ssh/id_dsa): (just press enter) Enter passphrase (empty for no passphrase): (just press enter) Enter same passphrase again: (just press enter) Your identification has been saved in ~/.ssh/id_dsa. Your public key has been saved in ~/.ssh/id_dsa.pub. The key fingerprint is: (some long key) The key's randomart image is: (a picture made of ASCII characters)

Now you just need to copy the contents of:
~/.ssh/id_dsa.pub to the file ~/.ssh/authorized_keys
… on any machines that you would like to be able to connect to (for example your server).