A sex position where one partner penetrates another parter, who is on his or her knees, from behind. If you have ever seen a dog hump something, it's like that. But seriously? Why ask that here? Just do a google image search, hahahahaha
I (personally) am a sport chic style. It's real in right now (FYI). There are many styles! There is T-Shirt and I-could-care-less (but no one, no one will ever make it through high school with that...
If by "service style" you mean "community oriented" then yes, those would be three styles (altho in other texts they are sometimes described differently).