An e-mail alias is actually an email that shares a mailbox with a totally different e-mail. For example, you can have email@example.com as well as firstname.lastname@example.org and e-mails sent to either one of them will be received in one and the same mailbox. This option will make it a lot easier and much more convenient to manage various addresses because you will have to log in to only one mailbox if you use webmail or configure a single e-mail address in a e-mail application on your desktop. If you create an alias, you won't just have the ability to receive e-mails, but you'll also be able to send e-mails from the various addresses and they will share the Outbox, so you will still have all communication in one location. Making use of aliases can be a replacement for making use of various e-mail addresses for various purposes or forwarding one e-mail address to another one in order to handle the emails of both in one location.