There are a few very popular dishes that are served and some really depend on your specific culture, upbringing, and location. Some things you will find at every Passover Seder include the items on the Seder plate. This usually consists of: a shank bone (or root vegetable to be veg), hardboiled/roasted egg, horseradish, charoset (apple and nut mixture), parsley, lettuce/bitter herb, saltwater, and matzah. You usually will also have red wine, gefilte fish, matzo ball soup, chicken, brisket, potatoes. Here is a fun coloring page for a Seder plate.