Eggplant is the main vegetable ingredient in the Greek version of moussaka.
Greek moussaka is a layered baked dish usually made with eggplant, minced meat, tomato sauce and a creamy béchamel topping. The eggplant forms the characteristic vegetable layer and gives the casserole its soft texture and savory flavor.
The modern Greek form was popularized in the early 20th century by Nikolaos Tselementes, whose cooking helped establish the béchamel-topped version familiar internationally. Other Balkan and Middle Eastern dishes called moussaka can use different vegetables, including potatoes or zucchini.
This regional variation explains why descriptions of moussaka do not always match. The answer refers specifically to Greek moussaka, not every dish carrying the same name. It is generally baked in a dish and cut into portions like a casserole.