You are not the first one to ask this question "Ienjoymusic" this question has been asked atleast a hundred times, and everytime the answer is going to be the same. Read articles on compressors and limiters. It is hard to explain a to z of compression, so please read more articles regarding that. I dont have a good article link to provide you now, but I am sure the one who posts after this woudl give you a good article to learn.