Andy is correct. A manifest train is a train that has every type of car in it. For example, when you see trains with box, tank, cushion-coil, gondola, hopper, autorack and any other car, that's a manifest train. On the Union Pacific, 25% of trains are manifest. Otherwise, they are unit trains which haul one specific commodity. So if you ever look at UP train's ID, if its first letter/character is M, that means it's a manifest. I don't know if the BNSF uses this system but I think they do.