I know a window pops up saying they will be notified and they get notified, but is that it? Is there a point to poking or is it just supposed to be fun? I heard somewhere that the person you poked can now see your page even if you're not friends. Is that true?
When you poke someone, they will receive a poke alert on their home page.
The Facebook Poke FAQ has more details.
As to the second part of your question, Friends of Friends (not necessarily your friends) or someone in your shared network can also send you pokes in addition to your confirmed friends.
The visibility of your profile pages depends on the privacy settings that you've set up.