Electricity is a type of energy that makes it possible to light our homes, offices, street lamps etc. A torch lights up because there is a bulb which glows because of electricity.
A torch uses an electric cell. Electric cells store chemicals that produce electrical energy. When you switch on a torch, the electric cell begins to supply electrical energy to the bulb, making it give off light. All the time the torch is switched on, energy is flowing from the cell to the bulb. Over time, the energy stored in the battery is gradually turned into light (and heat) in the bulb and the chemicals are getting used up. This is why the battery runs flat when the all the chemicals get over.
For electricity to flow, we need a circuit. A circuit is a closed path or a loop around which the electric current flows.