Relief printmaking has many different forms to it, with one unify principal.
Woodcut and linocut are two traditional forms (woodcut was one of the first ever forms of printmaking).
Taking an even surface, the printmaker will remove the parts of the image he wishes not to be printed, leaving the protuding surfaces as the ‘shown’ parts of the image. If using wood he will cut away from the wood using special carving tools.
They with a roller, he will carefully apply an even layer of ink to the sections of the blocks which remain.
As shown by this diagram.
With both of these techniques it is possible to create different layers of colours, with different printing blocks, building up shades and tones.