Selecting UVs, UV components, and UV shells is critical to editing the layout of UVs in the UV Editor. You can select UVs in either the scene view or in the UV Editor, but you can only view and edit the 2D representation of UVs using the UV Editor.
To select UVs in the scene
UVs for the surface mesh display in exactly the same location as vertices, so you can select them in the scene view.
The UVs are selected in the scene view. To view a 2D representation of the UVs you must open the UV Editor (UV > UV Editor).
To select UVs and UV shell components in the UV Editor