MOMA has a fabulous tutorial about printmaking:
Relief printing is a term used to describe the process of printing from a raised surface where the non-image areas have been cut away. Wood and linoleum are traditional matrices used for relief printing.
The process involves taking a block of wood or linoleum and cutting away the negative space, leaving the image in relief. The block is then inked, paper is laid on top and gently rubbed. The paper is peeled off and the image has been transferred to the paper.
Anyone who did a potato print in elementary school has made a relief print.
SCREEN PRINTING: SILK-SCREENING & SERIGRAPH PRINTING
Screen printing is a stencil method of print making in which a design is imposed on a screen of polyester or other fine mesh, with blank areas coated with an impermeable substance. Ink is forced into the mesh openings by the fill blade or squeegee and by wetting the substrate, transferred onto the printing surface during the squeegee stroke.