LCh is a variant of the CIELab color space.
L = Lightness
C = Chroma
h = hue angle
It is sometimes easier to visualize 3D color space in terms of LCh than Lab. In LCh, the further out from the center of the space you go, the more saturation (Chroma) is represented. Also the 'perimeter' of this 3D cylinder becomes a color wheel, which is represented by h (hue angle).
For this reason, some profile editors (Such as ProfileMaker's Profile Editor) allow you to edit in LCh space.