The wood block is a relief matrix, which means the areas to show 'white' are cut away leaving the image to show in 'black' at the original surface level.
The block was cut along the grain of the wood.
The block is inked and brought into firm and even contact with the paper to achieve an acceptable print.
The content would print "in reverse" or mirror-image.
For colour printing, multiple blocks are used, each for one colour, although overprinting two colours may produce further colours on the print.
Multiple colours can be printed by keying the paper to a frame around the woodblocks.