An e-mail alias is an email which uses exactly the same mailbox as the initial email address. For example, you can have email@example.com as the actual e-mail address and create an alias firstname.lastname@example.org. Each of the addresses can share the very same mailbox, so emails sent to both of them will be received in one place. You can use aliases for various reasons, for example getting in touch with numerous groups of people or registering on sites. If you ever start getting a lot of spam, for example, you can just remove the alias whilst your original mailbox won't be impacted in the least and you'll keep the communication you need. Aliases are often regarded as a replacement for forwarding messages from one mailbox to another one if you are using a couple of addresses for contact on your web site.