In previous versions of Photoshop, clicking the “Create a new group” icon at the bottom of the Layers panel added an empty Layer Group regardless of whether or not any layers were selected. In the current version of Photoshop CC however, with multiple layers selected, clicking the “Create a new group” icon adds a new Layer Group and places all selected layers into that Layer Group. Command + G (Mac) | Control + G (Win) will also create a new Layer Group while placing any selected layers within the Group.
To create an empty Layer Group, deselect all layers and click the “Create a new group” icon (Photoshop adds the group to the top of the layer stack).
To quickly ungroup layers, select the Layer Group in the Layer panel and use the keyboard shortcut Command + Shift + G (Mac) | Control + Shift + G (Win).