Pretty much as it suggests – the bevel is like a V, even on both sides and straight as a V. May just be a secondary bevel, sharpened from the "shinogi" (midline) or a combo of both.
The Offset V
60/40, 70/30, 52.6/47.4 – basically refers to the % of the bevel on each side as opposed to the angle on each side.
Generally offset with a flatter grind on the back side (LHS for right handers) and a more rounded clamshell edge on the front side. It may or may not be finished with ‘koba’ or final edge that may or may not be an offset V.
Clamshell edge. Basically tapers from the top of the blade in a curved "clamshell" shape. May have a secondary bevel for ease of sharpening. May be on the front side only.
As the term suggests there is a concave section in the blade, the benefit being it will slip through food easily without sticking – or so the theory goes. May or may not come with a secondary bevel.
Refers to "true edge" – there is no perceivable bevel because there is a gradual reduction in the thickness of the blade all the way from the spine to the edge. This is the ultimate way to grind a blade that is frustratingly hard to achieve and even harder to resharpen. Blades sharpened in this way can be resharpened with a secondary bevel for ease.