A cobbler is a deep, oven-proof dish with a filling topped with a thick biscuit dough topping and baked in an oven. The filling is usually sweet, and usually fruit, but sometimes savoury fillings are used to make it a main course instead of a dessert.
If the cobbler is a dessert, the topping is usually sprinkled with sugar before baking. Sometimes, the dish will be lined with the thick crust as well.
Cobbler originated in North America. Settlers didn’t always have the time, or the appropriate kitchen space, to roll out pie crusts. Sometimes they didn’t have ovens to cook them in. A biscuit crust could be mixed in a bowl, then pressed into a pot to line it. It could be filled with fruit, and then cooked by hanging the pot over the fire. Later, a variation emerged in which the crust was only on top, and that is what is more common today.