Use Layer Contents as Selections

Hold Ctrl (Mac: Command) and click on the layer thumbnail in the layer’s panel to load its content as a selection.

Holding Shift + Ctrl (Mac: Shift + Command) and clicking on another layer thumbnail will add to the selection and holding Alt + Crtl (Mac: Option + Command) and clicking on the layer thumbnail will subtract the layer from the selection.

To intersect the selection hold Shift + Alt + Ctrl (Mac: Shift + Option + Command) and click on the layer thumbnail.