A woodcut is a type of relief print created by carving away areas from the surface of a woodblock. The type of wood used will greatly determine the quality of the marks and image, from very precise, refined images, to aggressive, ragged marks and shapes. Many different kinds of tools can be used to carve the block, from traditional Japanese woodblock knives (each with their own unique shape and purpose) to chisels, gauges and even dremels and other power tools.
In a relief print, the ink sits on the surface of the block so the carved areas become negative space. Generally, one color is printed at a time. Additional colors can be achieved by carving another block for each color desired or by creating a reduction block print. In a reduction print, the block is carved with the image for the first color and then carved some more for each additional color. Since the block changes with each carving, you can not go back and reprint the edition from the start.