These pieces of glass are lit by shining LEDs into the edge of the pieces of glass; allowing the light to reflect off of the engravings from inside the glass.
These pieces are engraved, not etched. Engraving means carving with a tool such as a diamond cutting tool. The tool is held free-hand.
I do not do any chemical etching of glass in my art work because engraving has more life and does a much better job of reflecting light than etched glass.