Duplicating
There are a number of ways to duplicate data from one layer to another.
Duplicating an entire layer is as simple as pressing Command + J. If a
selection is active, you can use the same shortcut (Command + J) to create
a new layer based on the selected area of the original layer. Pressing
Command + Shift + J with a selection creates a new layer while cutting the
data from the original layer. Holding Option while pressing one of the arrow
keys allows you to duplicate the current layer and nudge it by 1 pixel.
Holding Shift and Option nudges the new layer by 10 pixels.