A Yorkshire pudding is a batter based (flour, egg, milk + water) thing you mix up, and bake in the oven in oil filled trays a bit like a muffin tray but shallower.
Usually served with the traditional British Sunday dinner, or with sausages in which is called Toad in the hole. Although some people including myself eat them as a dessert with jam, honey, syrup etc as they're basically a risen pancake so can be sweet or savoury.
There ends my culinary lesson for the day, come back tomorrow where I shall discuss pasties and Kendall mint cake
NB. The puddings you've seen with meat in them are called Suet puddings, usually Steak and kidney and steamed for about an hour or so. They're more of a main meal, not an accompaniment like the good old Yorkshire.