Yes you can eat ordinary mushrooms raw provided that they are cleaned. They are a tasty addition to salads but be careful adding dressing as they can soak up an amazing amount of oil. To cook, peel or wash depending on size, trim or remove the stem if woody, and fry quickly in a little of the oil of your choosing, I prefer butter or olive oil. Add a little chopped or pureed garlic towards the end of cooking. You can also add them to soups or stew, I prefer to cook them first, use as a topping for pizza or toast. If you are making a traditional english breakfast, then fry the bacon first and cook the mushrooms in the fat. I understand that morels, chanterelles and the japanese types of mushroom can only be eaten cooked. I am not fond of these so will leave someone more knowledgable than I to post instructions for cooking them