Be more confused. They are both mask they do the same thing. However they are create and edited with different tools. Layer Masks are pixel based a gray scale channel like raster gray scale image. You use Photoshop Pixel tools to create and edit Raster Layer mask. Vector mask are created and edited with Photoshop vector tools they are a vector graphic. Adobe Photoshop use mask several ways. Adobe introduce not to long ago a Frame mask these are very strange layers in the layers palette the Frame vector mask thumbnail is on the left side where the Layer's content Thumbnail should be it. To the right of the Frame mask is the Layer's smart object content thumbnail and to the right of the Smart Object layer thumbnail there can be a Layer mask thumbnail. A Frame Layer is a two for tit a last set and a layer layers in one slot. Layer can be Smart Object Layer that has a Layer Mask a Vector Layer Mask and a smart filter mask. Shape Layers have a Vector Layer mask but not vector mask thumbnail in the layers palette. Layers cans be groped into Layer set and they can have Layer Mask and Vector Layer mask. The can be man mask associated to a layer.

Above there are two layersets abr three layers.

