Cro stands for Central reservation office(I think), but they are the people you speak to if you phone Disney directly to reserve a room.
Annual pass is a year ticket you can buy at the Disney store, on line, or in the parks. It gives you admission into Disney for one year and you can also recieve a discount on your room if they are being offered at the time you are going. It is like any promotion, only a certain amount of rooms are allotted, so you have to be quick when they are announced.