A lithograph is a kind of print. Prints are made from an original piece of art by first making a negative of it. The negative is then made into a print plate. A print plate is made for each of the colors used in the design. The individual prints are then made by inking the plate and using a press to stamp them out. This process can be very complicated and expensive when it comes to making concert posters and art prints of the type we sell.
When the signature on the individual print is hand signed it means that the person actually signed the individual print. When the signature is called "Plate Signed" that means that the person signed the print plate which results in a printed signature on the individual copies.