Same kind of fast food as McDonalds in the sense that it's very casual (ie: it's not a proper restaurant), they have drive throughs, no waiters or anything, and it's fast and cheap. But In-n-out uses all fresh ingredients, cooked to order. So if you order fries, you can literally watch them slice the potatoes in front of you before deep frying. They also treat their employees really well and the prices are cheap cheap cheap. In-n-out has a cult following in California and is generally regarded as one of the best fast food places in America:
Top Fast Food Restaurants - Chef Reviews of Best Fast Food Restaurants - Esquire
Science Confirms In-N-Out Burger Is The Best And McDonald's The Worst
Subway, In-N-Out, Chick-fil-A top Zagat fast-food survey - latimes.com
So basically, it's fast food done right.