Email control panels allow instant creation of email POP3, forwards, and aliases.
A POP3 account is a stand-alone incoming email account. So, if you create u: john p: doe it all mail sent to firstname.lastname@example.org, it will be routed to the john email account. The user john can then check this mail by logging into webmail.domain.com using his username and password.
An alias forwards mail sent to one address to another POP3 account within your domain. For example if our recently created john account was going to receive all mail sent to email@example.com, we would setup sales as an alias to john.
Note: by default, all names are not configured to send to the root account. So if you sent a message to firstname.lastname@example.org it would not be sent to your main root account, unless you had set it up as an alias, forward or POP3.
A forward account forwards mail sent to email@example.com to an address completely out of your domain. For example if john had an AOL account and wanted to check all his mail there, you could setup john to forward to firstname.lastname@example.org.