Greyscale:

Greyscale is the value of each pixel in a single sample. It is where you choose the integrity between white and black in each pixel with grey being the central shade.

RGB:

An RGB colour space is any colour made between the three primary colours red, yellow, and blue. It is the triangle defined by those three primary colours.

YUV:

Luminance and chrominance (luminance being light and chrominance being colour) is the difference between brightness and colour. It started off as a encoded format which was often in digital video to give colours rather than just black and white.

HSV:

Hue, saturation and value are all different colour formats. Hsv itself is a colour model which describes colours. (Hue)