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 one pixel.
Holding Shift and Option nudges the new layer by ten pixels.