Everything so far totalled energy. Power asks how quickly it moved: $P = \dfrac{W}{t}$ — P equals W over t. $P$ is the power in watts, $W$ is the work or energy in joules, and $t$ is the time in seconds. One watt is one joule per second, and that is the entire definition. Carry a crate upstairs slowly or sprint it up: identical work, wildly different power.

There is a second road to the same watt. Substitute $W = Fd$ and $d/t = v$, and you get $P = Fv$ — P equals F v, where $F$ is the driving force in newtons and $v$ the speed in m/s it is delivered at. Use $P = W/t$ when the story gives you a total job and a clock; use $P = Fv$ when it gives you a force and a steady speed. Same relation, two doors.

The house trap of this lesson is the prefix. Motors, kettles and cars are quoted in kilowatts, and $1\ \mathrm{kW} = 1000\ \mathrm{W}$. An answer in kilowatts poured into a box marked watts is off by a factor of a thousand, which is not a rounding error — it is the difference between a hair dryer and a locomotive. Convert at the END, never inside the formula.