Bandz-
Welcome to the site
Yes, they use hops in Guinness.
The amount and TYPE of hops as well as the amount of time they spend in the boil all contribute to the bitterness, flavor and aroma of the end beer.
These factors vary from beer to beer and style to style.
Some styles of beer contain very few hops. Others, like IIPA contain insane amounts of hops (on the order of 5 or 6 lbs per barrel). Usually those are citrusy American hops in an IPA or an American Pale Ale like Sierra Nevada or Mirror Pond. Sam Adams Boston Lager uses German Noble hops, which are spicy and lighter in flavor and aroma.
English/Irish/Scottish beers use British hops and those tend to be earthy.
I'd suggest you take a look at this web link to get an idea of how hops affect the final beer:
http://www.howtobrew.com/section1/chapter5.html
Also, go to this link to read up about all the various beer styles and how they taste, smell and feel:
http://www.bjcp.org/2008styles/catdex.html
Hope this helps-