Complex sentence: A colour look-up table (CLUT) is a device which converts the logical colour numbers stored in each pixel of video memory into physical colours, normally represented as RGB triplets, that can be displayed on a computer monitor.
Split into simpler sentences: A colour look-up table (CLUT) is used to transform a range of input colors into another range of colors. The hardware color look-up table will convert the logical colour numbers stored in each pixel of video memory into physical colours, normally represented as RGB triplets, that can be displayed on a computer monitor.