light
I started to replace a light fixture in a closet and discovered that although 2 wires (each containing a black, white, and ground wire) come into the box, only the white wires are connected to the fixture (one on each side). Black and ground wires are connected separately, but not attached to the fixture. See picture.
The light is controlled by a single switch. How can the light work (it does if the switch is turned on) without a black wire?
The group of 3 white wires is your neutral bundle. Add the white wire from the new switch to it.
The group of two blacks is probably hot and a feed thru, connect both with the black from the switch.
Connect the remaining black (likely your load) to the blue wire.
Ground to ground. And I bet you have it in the back of the box. (The house looks new enough)
The symbol you described sounds like ground:
This should connect to the bare wire in your box. All white wires together, all green/bare ground wires together, and the black/L wire to the black wire in the box.
If your fixture has both a bare copper wire and a green insulated one, the green may be to connect different pieces of the fixture. Check the instructions, perhaps it should be bonded to another point on the fixture rather than to the supply wiring.
Finally, do not wrap your ground wire around the other wires in your box. Ground should be kept separate, you don't want to inadvertently have it contact the hot wire (instant short) or neutral (a hard-to-detect failure of the safety ground).
Best Answer
It looks like a switch loop that was wired backwards. The always hot of a switch loop should be white and the switched hot should be black with a marking on the white always hot to identify it as a hot. I have seen this many times, it is easy to fix by swapping the white and black at each end and then marking the white wire with a black sharpie or black tape (any color other than green, gray or white would meet code)