This warm-white glowy letter "A" is made out of COB (chip on board) LEDs, often seen in 'Edison-like' LED bulbs, arranged in different patterns to give a bright, warm lighting effect. They're made of dozens of micro LED diodes that are bonded together on a stiff metal backing and then coated in silicone for protection. Even though the LEDs are only placed on one side, the PCB substrate is very thin so it glows out the back too (although a little dimmer)