The name already says it all.
20 is for 20 bulbs of 12V 50W in a special sealed beam raylight with a GY6.35 lamp base, which makes it easy and cheap to replace when a lamp is broken.
3 is for three movements, which makes it as versatile in use as an Clay Paky Astro Disco 3.
It came with a sturdy flightcase and is in a remarkable good shape
Here's an impression of her test run just of of hybernation