The two players in a game of chess are identified by the colour of the pieces they are using.
The sets of pieces are made from materials of two contrasting colours, conventionally referred to as black and white.
Most everyday chess sets actually are black and white.
The chess player who is using the lighter-coloured pieces is conventionally referred to as white.
The chess player who is using the darker-coloured pieces is conventionally referred to as black.
A diagram of a chessboard is conventionally positioned on a page such that white is at the bottom, playing upwards towards black, and black is at the top, playing downwards towards white.