He starts off okay when he states
But from then on I think he goes into the weeds when explaining horsepower.
Short explanation of power
Power is the speed at which the torque is applied.
How much torque can we maintain on a spanner, if the spanner is turning at 2000rpm?
When we know this torque number we can calculate/extrapolate the power being applied to the spanner, at 2000rpm.
Its just than simple.
What is the difference between torque and power?
Torque is the force. Power is the rate at which we can apply that force.
StrikeEngine has a number of calculators related to power and torque
Measure engine power without a dyno