The memory bolted onto a graphics board so the graphics processor can pull drawing data at high speed. It shares its roots with desktop DRAM but is tilted toward moving a lot of data at once, and generations are named GDDR6, GDDR7 and so on. Because it competes for the same fab lines as server DRAM, it gets pushed back and repriced whenever server demand runs hot. That is usually why graphics card prices move without any change in performance.