Simply put, the power band is the rev range where the engine makes the most power.
Basically, every engine is efficient (produces the most torque) through a set range of revs. Below that range, and it struggles to push you, too high and the power peters off and you aren’t accelerating as fast as you could be (usualy happens close to the redline).
The simplest way to know your powerband is to play with your throttle at various engine speeds. If you are toodling along at 2000rpm (below the powerband of most bikes) you can give the throttle a sharp quick twist and not much will happen (if you hold the throttle steady, you’ll feel the acceleration “build up”, or get stronger as the revs climb). But if you try the same thing in the power band the bike will accelerate cleanly (no “building up” of acceleration, it just goes).
Be careful doing this on the CBR1000RR. Its has enough torque that even when you are technically below its powerband (but above the minimum useful revs) it should still pull cleanly. If you give it a whack of full throttle while in the powerband it WILL lift the front end.
“The two seconds between ‘Oh S**!’ and the crash isn’t a lot of practice time.”