The functionality to Hide Faces to see less detail or inside a body. Also, edges that are connected only to hidden faces will also become hidden. Hidden faces/edges cannot be selected. Likewise vertices with all their faces hidden cannot be selected. Show Faces is used to restore their visibility. Note that if you set Tools>Options>Graphics>Show Edges of Hidden Faces to Yes, then the edges will not be hidden, and both the edges and vertices will be selectable.
Note that the Hide/Show Faces options only apply to bodies that are not suppressed and not marked as hidden.
Context Menu Options
Hide Face(s): When faces are selected in the Graphics area, this will hide the selected faces.
Hide All Other Faces: When faces are selected in the Graphics area, this will hide all faces in the model, except the selected faces.
Show All Faces: Right clicking on Show All Faces resets the visibility of all faces in the model to visible. If any bodies, faces, edges are selected prior to choosing this option, then only hidden faces on the bodies of those selections are reset.