Well that's part of it, but there's also this added dimension:
getting every email sent @mydomain.com to forward to single address.
So, for example, if I set up an account on "genericnews.com," I can give them the email address "email@example.com" Any email they send me (or anyone they give my email to!) is forwarded automatically to my main email address without me having to have manually set up firstname.lastname@example.org beforehand.
There is an option in google apps to forward messages sent to non-registered accounts to a specific account, but then it doesn't show me what address it was sent to!
You see, this is my desired result:
I have a personal email account that I use to check my mail. When I give out my email address I can give them a custom address @mydomain.com. All messages sent to my domain is forwarded to my personal account. Once there I can use filters to organize my mail, so I could view everything sent to email@example.com separately from firstname.lastname@example.org
Finally, although this seems less possible, I'd like to be able to reply as the account they sent my mail to.
Hope this clarifies, as I said, I'm a little new to this. D: