Originally, power refers to one’s ability or possibility to do something.
In mythology and fiction, having powers means being able to do magic, to use supernatural forces, to get what we want. Most of the time, a magic power can be used to do good or bad, according to the intentions of the one who has this magic power.
Power can be many different things.
First of all, there’s power as the ability to rule (cf sovereignty), which gives us a certain authority that makes others obey (see obedience). This type of power can be legitimate, for example a president who’s elected by citizens, or illegitimate and imposed, for example when someone makes a coup and puts themselves as a leader of a country.
We often associate power with violence, because the one who possesses power can use violence to force other people to obey and to inspire fear. Fear can be a way of pressure to force obedience. We can talk about abuse of power when someone who has a certain power starts to use it to do bad stuff and to get even more power.
However, power is not a negative thing, just like magic we just have to use it wisely (see wisdom) and with good intentions. We don’t have to be a leader to have power.
Having power is also having the possibility to change a problematic situation : for example, we have the power to change someone’s life by helping them (see empathy), or to improve the environmental situation (see eco-conscious).