Purpose of email at the end of SSH public key

I was adding one of my public keys to the authorized_keys on one of my servers when I realized that at the end of my public SSH key there is my email:

$ cat .ssh/id_rsa.pub
ssh-rsa AAAA[...lots of characters...]bpL [email protected]

• Why is my email address at the end of the key?
• Does it have any specific purpose?

• Can I write anything I want in my authorized_keys file? Like for instance:

  ssh-rsa AAAA[...lots of characters...]bpL John Doe (Home PC)
  

1. Most likely to identify who created the key.

2. It is just a comment. But as said at 1: probably so you know you created it. Useful when more than 1 administrator is administrating the system.

3. Yes, you can add anything in place of your e-mail. And since it is the last part of it you do not have to use anything special for spaces etc.

   Extra: ssh-keygen -c to change it for RSA1 keys (only works for RSA1).