HSB is actually far easier to understand than RGB, so that's good.
I actually wrote a stupidly long post explaining HSB, so I'm quoting a bit from there, but interspersing to answer your question more specifically.
What is Hue? Think: "Color of the Rainbow"
Hue is a number between 0 and 360. It’s measured in degrees, like degrees of a circle (because whoa, spoiler, circles also have 360°). Remember the color wheel? Hue is just where you are on the color wheel.
What is Saturation? Think "Richness"
Saturation is a number between 0 and 100. So, no matter what hue you’ve picked, a saturation of 100% will be the richest possible version of that color and a saturation of 0% will be the gray version of that color (i.e. if the color is light, it’ll be a light gray; if the color is dark, it’ll be a dark gray).
Saturation is pretty simple. I sometimes think about it as the amount of color injected into the gray. So 0% is a flat gray, but 100% is the most colorful color your monitor can make.
What is Brightness? Think of a lightbulb
Brightness is a number between 0 and 100. Like saturation, it’s sometimes written as a percentage. This one is fairly obvious as to what it means, but there’s a quick catch.
0% brightness is black, no matter the hue, no matter the saturation.
100% brightness is white only if saturation is also 0%. Otherwise, 100% brightness is just a… very bright color.
Sound confusing? Think of it this way. Imagine Brightness is a lightbulb. 0% means the lightbulb is off (pitch black in the room). 100% means the light is on full strength. So maybe 100% brightness is a bright color, or, if the light is already white, then 100% brightness is pure white.
Is black on the color wheel? No, but it's on the color cylinder
A wheel is flat, so it's in 2D. The HSB "space" of colors has three dimensions (H, S, and B... surprise!), so it's a 3D shape. In our case, a cone will do just fine.
Black is the ENTIRE color wheel where brightness=0. So, no matter what hue you have, no matter what saturation you have, if brightness=0, you're looking at BLACK.
(Oddly, white works differently. White is only one point, NOT an entire color wheel. To get white, you have to have brightness=100 AND saturation=0. That being said, there's a color system incredibly similar to HSB, but the only difference is it makes white and black exact opposites. That system is called HSL – hue, saturation, lightness.)
How does my skin tone change with lighting?
This question is more thoroughly answered here, but basically, the hue, saturation, OR brightness of your skin could change with the lighting.
- HUE: If your normal skin hue is between 0° and 60°, then in bright (white) lighting, the hue of your skin will shift towards yellow (hue=60). In darker lighting, it will shift towards red (hue=0°).
- SATURATION: In brighter lighting, your skin will have lower saturation. In lower lighting, it will have higher saturation.
- BRIGHTNESS: In brighter lighting, your skin will have higher brightness. In lower lighting, your skin will have lower brightness. But... you already knew that, didn't you? ;)
Hope that helps!
You can find a few more details here