throughput
termnetworking
How much data actually gets through per unit of time - as opposed to the link's rated capacity, which is a ceiling and not a promise.
The gap between the two is where the interesting questions live. A gigabit link carrying a single TCP session across a continent will not reach a gigabit, because the sender may only have one round trip's worth of data outstanding at a time. That is why the fix for a slow transfer is often a larger window or more parallel streams rather than a bigger link, and why buying capacity to solve a distance problem is the most common expensive mistake in the field.
Also known as: bandwidth, goodput