Check out any standard AI work for a detailed explanation. Here's some inspiration on what's been done with them (back in the day anyway...if you check out this

Check out any standard AI work for a detailed explanation. Here's some inspiration on what's been done with them (back in the day anyway...if you check out this company their product is used in blockbuster games like GTAIV): http://bit.ly/k30h02 http://bit.ly/k30h02