Hsv (also known as Hsb) is similar to Hsl. They're both based on cylindrical geometries, but Hsv is based on a "Hexacone" model while Hsl is based on a "Double Hexacone" model. Read more about the differences on wikipedia.
Xyz is an additive color space based on how the eye intereprets stimulus from light. Unlike other additive rgb like Rgb, Xyz is a purely mathmatical space and the primary components are "imaginary", meaning you can't create the represented color in the physical by shining any sort of lights representing x, y, and z. It's complicated to explain in a nutshell, so read more about it here:
If you're into color, color theory or design you should definitely check out the award winning Nix Color Sensor. It really is a game changing tool.
Color conversions performed using the open source ColorMine library.