An email alias is actually an e-mail address that shares a mailbox with a completely different email. For instance, you can have firstname.lastname@example.org plus email@example.com and emails sent to both of them will be received in a single mailbox. This feature will make it much easier and more convenient to manage many different e-mail addresses as you will have to log in to just one mailbox if you work with webmail or configure one single address in an e-mail client on your computer. If you set up an alias, you won't just be able to receive e-mails, but you'll also be able to send e-mails from the different addresses and they will share the Outbox, so you will have all communication in one location. Using aliases is an alternative option to using various e-mail addresses for different purposes or forwarding one address to a different one in order to handle the emails of both in a single location.