They sound like what I have all over. I've been told that it's because the pigmentation in my skin didn't spread evenly and that I have high concentrations of pigment in certain areas (hence the little brown dots). Most of them are small, like darkened freckles, but they aren't raised like moles. They aren't really anything to worry about unless they're causing you pain/are itching/bleeding. As to how to get rid of them though, there might not be anything you can do. I had a large one on my arm that was bothering me and a dr took most of is out with a miniature cookie-cutter (that was fun), but in the end it came right back. If they aren't exceptionally large and causing you a great deal of discomfort (physically or mentally) then I would just view it as a part of what makes you unique. If they are bothering you though, go talk to a dr and see what they can do