You may as well have asked "What church should I go to?" because there are as many answers to that question as the one you asked
There is no set diet we follow on this site. There are a lot of vegans and Atkins followers here, and a lot of people who are somewhere in between.
The simplest answer is, avoid prepackaged and eat fresh whenever possible. Doing this is going to reduce your fat, sodium, and processed/simple carbs dramatically. Also avoid white foods (white bread, white rice, white potato, white pasta). I personally like to stay above 20% protein, and closer to 30% when I can manage it because I feel less hungry and my blood sugar is more stable, but that's a personal choice which may or may not work for you.
Proteins, carbs, and fat are found in every food. But generally things like meat, eggs, and dairy are considered proteins. Vegetable proteins are things like nuts, seeds, beans. Most protein sources also have considerable amounts of fat, which is why it's important to get the leanest cuts of meat you can find, and using egg whites instead of the whole egg cuts out fat because that's mostly in the yolk.
Fat has more than twice the calories per gram than proteins or carbs do, which is why a lot of diets are "low fat", you get to eat a bigger meal if you cut the fat out. But fat is also where most of the flavor is, so "low fat" prepackaged foods are often packed with sugar and salt so they don't taste like cardboard. Fat is also vital to many body functions, so you don't want to go too low. Just make sure they come from healthy sources-vegetable fats instead of meat fats. A simple rule of thumb is bad fat (like butter) is solid at room temperature, and good fat (olive oil) is liquid at room temperature.
Carbs are the main source of fuel in our food. There's two main categories, "simple" and "complex". Sugar, corn syrup, and anything "white" falls into the simple category. Simple carbs are absorbed very quickly, which spikes blood sugar, makes you feel hyper for an hour, then the sugar's all gone and you crash, making you feel tired and wanting more sugar. Complex carbs are whole grains, fruits, and veggies. Things with high fiber. Complex carbs take longer to digest, so the sugar in them is relased slowly over time. You dont get the spike and crash feeling.
I hope that helps. It sure is overwhelming when you are first getting started. Nutrition is not a simple thing, but it gets easier as you go.