An e-mail alias is an e-mail which uses the same mailbox as the initial e-mail address. For instance, you can have firstname.lastname@example.org as your actual address and create an alias email@example.com. The 2 addresses can share exactly the same mailbox, so messages sent to both of them will be received in a single place. You can use aliases for various reasons, like getting in touch with various teams of people or registering on web sites. If you start getting a great deal of spam, for instance, you can simply delete the alias while your original mailbox will not be affected in the slightest and you'll keep the communication that you need. Aliases are often perceived as an alternative to forwarding messages from one email address to another if you work with 2 or more email address for contact on your site.