We often use the word ‘power’ in our common usage to describe something strong and full of energy. However in physics, power has a very specific meaning. It is described as the amount of energy transferred per unit of time. As you know that unit of energy is joule.
Power is defined as:
Power = Change in Energy / Change in Time = joule / second = Watt
Hence the unit of power is Watt which was named after James Watt.
You might have remembered from the previous article https://geniuslittles.com/understanding-how-much-energy-is-contained-in-1-joule/ that 1 Joule of energy is roughly equal to the energy required to lift an apple at a height of about 1 meter. So if you lift an apple at a height of 1 meter against gravity and do this act in 1 second, then the required power is about 1 W.
Lifting an apple at a height of about 1m in 1s will be equivalent to 1 watt of power.
Similarly, if an electric bulb has rated power of 10 W then it means that bulb takes 10 joules in 1 second, when it is switched on.