Many times when we're debugging software or testing new functionality, we need to use an email address to register, over and over. Well, rather than create multiple accounts over and over, you can just use Gmail.

Let's say your email address is:

james@gmail.com
(it's not because they require 6 letter minimum so this is a good example)

If you append a plus sign (+) after your username, but before the @, you can enter any number or combination of characters and you will still receive the email at your normal Gmail address. For example:

james+test@gmail.com
james+test1@gmail.com
james+test2@gmail.com
james+testOneMillion@gmail.com

All of these would be delivered to james@gmail.com and save you from having to create one million email addresses.