Breakfast is the first meal of the day. You can have all sorts of different things for breakfast. Many people have cereal with milk or toast with jam or honey. Some people prefer a cooked breakfast with bacon and eggs. Other people might like waffles or pancakes.
And some people like a breakfast with almost everything, like in the picture.
Dinner is the meal you eat at the end of the day, usually at around 5 or 6 o'clock. Dinner can be anything, but is usually some kind of meat and some vegetables.
Lunch is a meal you eat in the middle of the day. Most people have sandwiches for lunch, but you can have almost anything. Some people have salad for lunch, other people will have a steak.