Woodblock printing is a technique for printing patterns used widely throughout East Asia and originating in China as a method of printing on textiles. The earliest surviving examples from China date to before 220 AD.
The wood block is carefully prepared as a relief pattern, which means the areas to show 'white' are cut away with a knife, chisel, or sandpaper leaving the characters or image to show in 'black' at the original surface level. The content would of course print "in reverse" or mirror-image. For colour printing, multiple blocks are used, each for one colour.