What we are seeing when we see an object is reflected light.
When light hits an objects, some wavelengths are absorbed and some are reflected.
Light of different wavelengths looks like different colors to us.
For example red
But BLACK and WHITE are a bit different from other colours, white is a combination of all colors, so when you see white, the object is reflecting all the colors of the light
Black is the opposite, it is the absence of all colors, which means, all colors are being absorbed.