Explain the differences between subtractive and additive color?

Subtractive color is the mixing of paints, dyes, inks, and natural colorants, etc. to create a range of colors; for example red and green pigments, being quite far apart, when mixed result in a dark browinish color depending on the actual pigments used.

Additive color is the mixing of illumination, a good example is the screen you are looking att now. There a yellow color is obtained by illuminating a green and a red sub-pixel.