All Denver Web Host accounts come with both e-mail aliases (also called forwarding) and e-mail POP accounts. Both provide e-mail services for you but work a bit differently.
What is the difference between an alias and a POP email account?
Here's an analogy, to help you understand this better:
A POP email account would be like your mailbox at your house. You would use an email program to retrieve the email for the account, just like you would use your mailbox to retrieve your mail.
An alias, on the other hand, would be like a mail forwarding address. An alias forwards your email to a POP account as a mail forwarding address forwards your mail from another mail address to your mailbox. Once it is in your mailbox, or POP e-mail program, you check it there.
A POP account is the final destination of e-mail, whereas an alias forwards your mail to that final destination. The reason you would want to use an alias or POP account is because it looks more professional and "cutting-edge" for people to write to youralias@yourdomain.com rather than yourusername@yourisp.com.
Of the two methods, aliases are the most used and easiest to setup. They do not require anything special to be done for software configuration and all e-mail sent to a given address merely ends up in your normal ISP's mailbox.