It's true that izakayas serve alcohol, usually in a wide array of drinks. However, that's not the best reason to go to one. The real appeal of an izakaya is the food. Izakayas generally have an extensive menu. At Nanda-Kanda, a mom and pop izakaya near my apartment, the name and price of each item is written by hand on a strip of paper, and these strips of paper cover every inch of available wall space.
People usually visit izakayas in groups.
Izakaya servings are usually very small. That way, everyone can nibble a dozen different items while drinking their beer. Dishes range from simple French fries to elaborate assortments of sashimi. One of the most popular categories of izakaya food is yakitori. Strictly speaking, this is grilled chicken on a stick, but it can be made with chicken and vegetables or even pork or beef.