There are three major nutrients, which we find in our food. These are Carbohydrates, Protein and Fat.
Carbohydrates(abbreviated: Carbs) are different kinds of sugar structures. Carbs are the main source for energy production in our muscle cells. If carbs are stored in muscle cells it's called Glycogen.
If we talk about Carbs in a food context, we distinguish three different kinds of Carbohydrates:
Protein is existing of different combinations of amino acids. It's used to repair (muscle) cells in our body. But their building blocks - the amino acids - have much more useful functions in our body.
We distinguish between slow and fast digesting proteins. A fast digesting protein is whey protein. Whey protein needs just 30 minutes to release its amino acids into humans blood stream. Through this it's an excellent post-workout meal to give the body quickly the opportunity to repair muscle cells traumatized from any kind of work out.
Casein is the slow digesting alternative. It needs longer to be available in the blood stream than whey protein but it provides amino acids over a period of 4-6 hours, when whey already peaked and is no longer available after 2-3 hours. This characteristic makes it predestined to be consumed over night, when the body rests and has nothing to feed on except its on muscle cells(neoglycogenesis).
Fat has no good reputation. May it be in the mind of people, who work out or not. People think "Fat makes fat" but that's a wrong conclusion. Once again we have to take a closer look. Fact is that fat is a high energy nutrient with 9kcal per gram. Compared to carbs and protein with 4kcal each it's really a heavy-weight.
We differentiate satured and unsatured fat acids. And then we have as well trans fats.
If we call some of these kinds "bad" then it's definitely the trans fats. These kind of fat you'll find in a lot of industrialized foods but they are not healthy at all. They are directly correlated with cardio-vascular diseases and you should avoid them in your diet.
You should integrate some satured fat, which your body needs for different processes.
What you should definitely incorporate in your diet are unsatured fats. You can categorize them into Omega-3, Omega-6 and Omega-9 fat acids.