Need help understanding Camera Lenses?

I was hoping that someone might be able to put into simple terms what an "AL" Lens is ? I have an older Praktica MTL-5 35mm with 3 M42 Mount lenses and would like to bring them over to A DSLR camera body with the aid of a Bayonet to M42 converter adaptor. They are A Vivitar 75-205mm zoom, Pentacon 108mm Telephoto, and a Penticon 50mm, and of course a Sologor 2X tele-converter. I would prefer to go with Nikon, but I think the chart says Manual focus "AL" lenses are not compatible, where other types are... Could someone please explain to me what this is ? or have any other suggestions on what DSLR Camera it could go with ?