Hue is the component of color that is most obvious. It is the redness of the color, or the blueness. It relates to the actual wavelength of the light, which is bounced off a particular object or surface. The easiest way to show the hue component of color is with a color wheel. Hues on opposing sides of the color wheel are deemed complementary colors, such as orange and blue.
Value refers to the part of the color having to do only with lightness or darkness. For instance, purple, aside from the difference in hue from yellow, is naturally darker. It has a darker value than yellow. Red and green are far apart in hue, but relatively close in value. Value is viewed as a distinct characteristic. You can easily see the values alone of different colors, if you have access to a photo editing computer program, by changing an image to gray scale mode.
Saturation is the third component of color. It concerns how richly hued a color is. A red that is fully saturated will be intense, like a ripe apple. A dull gray with a little red mixed in is still red in hue, but not as intense. It has lower saturation. You may see the terms intensity or chroma. These terms are synonymous, with regard to color theory, with saturation.
A good tool for practicing analyzing colors for their components is a Munsell chart. Have a look at a color, and determine how light or dark it is. What is its hue, or if it is between hues on the color wheel, which hues constitute the color? What is the saturation of the color? Is it rich and full of color, or closer to gray? The Munsell chart gives a visual diagram of how these three components work together.