apt, dpkg, dselect, and deity?

[Chris R. Martin]

Forgive me, I've been out of the Debian world for a while. I'm having 
trouble figuring out the relationship between apt, dpkg, dselect, and 
"deity" (which seems to be something in development). I know what dselect 
and dpkg are; dselect acts as a frontend (or used to) for dpkg. How does 
apt and deity fit into that picture? Are they replacements? It seems like 
dselect uses something called "apt-get" now for ftp and such, but why is 
there a dpkg-ftp package?

Thanks for any light you can shed on this.
Chris