An email alias is an email address that shares a mailbox with a completely different email. For example, you can have email@example.com plus firstname.lastname@example.org and messages sent to either one of them will be received in a single mailbox. This option will make it a lot easier and much more convenient to handle many email addresses since you will need to log in one single mailbox if you use webmail as well as create only one address in a e-mail client on your desktop. If you set up an alias, not only will you be able to receive messages, but you will also be able to send out messages from the different addresses and they'll share the Outbox, so you will have all communication in one location. Implementing aliases is surely a substitute for making use of different email addresses for different purposes or forwarding a single address to another one to be able to handle the e-mails of both in one location.