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 clicking on the layer thumbnail.