[Q] Catch-all host in DNS

[Netfortius]

Could someone be kind enough to point me to some good documentation as to how 
and what about catch-all host in DNS? I am interested in fundamentals, as 
much as implementation. 

I have been suggested by a blog vendor to implement a catch-all host on my 
name servers, but I am not sure how this would work, as far as the purpose 
for such from a blog stand point (but this would be a second question, 
unrelated to DNS, of course ;)).

TIA,
Stef