What is the difference between the memory interface, and memory size for graphics cards?

Just curious.

What is the difference between the memory interface, and memory size for graphics cards?
Memory interface is measured in bits (like 64,128, 256) and higher number indicates fater (sometimes much faster) performance.





Memory size is measured nowadays in megabytes (also 64, 128, 256...) and has little effect on performance. However, many games have certain requirements for the memory size and wouldn't run if it's less.