It's the nearest thing on the menu to having a complete meal on a plate as you would in England, but beware it will not be meat and 3 veg, like you are used to.
It is as it says, a plate of combined food, and can be a bit of what ever is on the main menu that day. Sometimes the restaurant will be serving a special.
One of the best combinations I had was Serrano Ham, Manchego Cheese, Pork Sewers and Croquet's.
You can put anything on the plate, it's ideal for using bits up that are in you fridge as anything goes.
Last weekend whilst watching the F1 we had a plato combinado consisting of - Bean Salad, Ensaladilla, Rice, Beetroot, Olives, Banana Chutney, Tuna and served with crusty bread.
A few more ingredients would be Chicken, Prawns, Chips, Papas arrugadas, Lettuce, Tomatoes really anything goes, just put a plate of different interesting food on the plate.
As I said it's a really good way of using up bits and pieces that you have in the fridge.