They are chips dedicated to graphics processing or floating point operations, allowing to lighten the workload of the processors when playing video games, interactive 3D applications or mathematical calculations. We can find them in specialized expansion cards, also called graphics cards or integrated in the same package of the processor.
gm is the short form writing for good morning. Used extensively within the crypto community where individuals greet each other casually. On the other hand, good night (gn) is used when people sign off for the day.