Gel markers

Okay, I know this isn't new to most of you but it is to me! I got a book out of the library about Altered Imagery and I thought I'd try a few things out of it. Of course this wasn't in it but the author was talking about gel markers so I had to run right out and buy some (of course!). The gel markers do really cool things to magazine images and photographs - like the colorize effect in Photoshop. Do regular markers do this too? What's the difference between gel markers and regular markers? I made this one to swap (it's my daughter with a king salmon) but I might just keep it for a while ...