DRAM
Beginner
The chip’s big main memory, usually on separate chips. It holds a lot but takes a long time to reach.
Novice
Dynamic RAM, a computer’s main memory. It stores each bit as charge on a tiny capacitor, which makes it dense and cheap, and it sits on separate chips or is stacked in the same package. Reaching it takes tens to over a hundred nanoseconds, many processor clock cycles. Its peak bandwidth is the width of the connection times its data rate.
Expert
For the architect it is a budget of bandwidth and latency. Sustained bandwidth is well below the datasheet peak because the memory pauses to refresh its cells, requests collide on the same internal bank, and the bus loses time switching between reads and writes. The controller and its PHY (the circuits that drive the off-chip wires) also take die edge and power.
Explained in Architecture (Design Flow).
See also: Memory hierarchy, HBM (High Bandwidth Memory).