whacky punctuation dealies

Say I have a command that looks like this:
host=$(/usr/bin/host xxx.xxx.xxx.xxx)

What is the significance of the $()
I know what happens when I don't include them, and I know what happens when I do, but...
Why doo it woik wit $()

Sorry for the lame question :o

do 'man ksh' and search for 'Command Substitution'

or 'man bash' if you are using bash, and don't have ksh, and search for the same thing.

D'OH!

Thanks for the quick responses. I was aware of the backquote method (aka "old-style") and didn't think to check the man page. :eek:

That'll larn me.