Cobblers were created during the colonial period in America as a variation on the pies that had been around in Europe since at least the middle ages. Without access to brick ovens traditional pies were difficult, if not impossible to bake, so cooks began to cook their pie filling in a pot over a fire and then placed the dough or batter just over the top. They would then cover the pot and let it cook further over the fire. Ingredients would vary based on local availability, and might include any kind of fruit, vegetable, or even meat. Eventually, the word cobbler came to mostly refer to a dessert and lost its association with savory dishes.
A stewed filling (usually of fruit) topped with a dough or batter and cooked until the juices are thickened and the pastry is baked through.
Ingredients vary based on availability and personal tastes, but a basic fruit cobbler would include fruit, sugar, spices (optional), flour or cornstarch for thickening the juices as well as flour, sugar, milk, and butter for the topping.