Need Help in BIND Download - Obscure Filenames

[tnaves at linkwest.net]

I need some help deciphering which files are what.  I want BIND 8.1.2 so I
downloaded the following files:

bind-8.1.2-contrib.tar.gz
bind-8.1.2-contrib.tar.gz.asc
bind-8.1.2-doc.tar.gz
bind-8.1.2-doc.tar.gz.asc
bind-8.1.2-src.tar.gz
bind-8.1.2-src.tar.gz.asc

I understand the following:

src = source code
doc = documentation

My questions:

What is contrib?
What is asc?

Obviously I am not a unix adept.

Thanks,

Tom Naves