phillipdale

I'm new to all of this and am trying to figure out just what an MP3 is. Both my 16 and 14 yo boys want one. I have one on my phone, but never use it. What should I be looking for? If it has a hard drive will it skip like a portable cd player does sometimes? Will a hard drive work good even when they are riding bikes and skateboards? I saw the Phillip's link and those prices look really good. Has anyone had a Phillip's? Is it any good/ Thanks for all the help.