You can make plantains in a variety of ways.
The simplest ways are to fry them. You don't have to deep fry them either. You can have them ripe, which will make them very sweet or green, which will be a more savory flavor (add salt after frying).
Also, you can boil them and mash them, green or ripe, you can also add them to soups.
Each country that cooks with plantains has a variety of ways of eating them, including dipping sauces, adding meats on top of the plantains. There's even "plantain nachos" that you can make, substituting them instead of the chips (after they are fried, of course).
You can also bake them, which is the way that I like them the best. I only like ripened plantains baked, however. Very delicious, 375 degrees or higher if you're watching, and depending on your oven, 20 minutes or so, they should be done.
It's a versatile food, but I count it as a starch, not a vegetable.