An email alias allows users to have different email addresses for different purposes without creating multiple accounts. With Google Workspace, users can create up to 30 aliases per account without affecting their monthly bill. Gmail also offers an alias trick that enables users to have multiple aliases without setting up additional accounts. Email aliases can be used to receive messages without revealing the primary email address and can be set up with filters to automatically move or label incoming emails. However, there are limitations such as not being able to send emails from the alias by default, not being tied to a Google account for certain apps, and not being private. To create an alias in Gmail, users can add it to their Gmail account through the Admin console or use the plus sign trick with Gmail aliases.