When you eat a meal, you sit down and dine on food. Breakfast is usually the first meal of the day, but if you oversleep your first meal might be lunch instead.
You can use the word meal to talk about the occasion (like dinner or brunch), or about the food itself. For example, you might say that chili and cornbread is your favorite meal during the colder months, or that a fast food hamburger eaten in the car is a poor excuse for a meal. Yet another meaning of meal is "edible ground grain or beans," like cornmeal or soybean meal.