Power is the rate at which work is done or energy flows.
Same amount of work can be done as long as same amount of force is applied and same amount of distance is traveled. However, one can do the same amount of work faster than others. Thus that someone is more powerful than others because power is the rate at which work is done.
Power equals to work divided by time. Because work's unit is joules and time's unit is seconds, one watt of power equals to one joule per second. Another unit of power that is often used for engine power is horsepower. One horsepower is euqal to 746 watts.