Cell can mean different things, depending upon which specific discipline of science we are talking about. In biology or microbiology, we refer to cell as the basic structural unit of all the living organisms. Our bodies are made up of cells and so are the bodies of animals and plants. Other commonly known cells are bacteria, some of which cause disease (pathogenic microbes).
In other common usage, cell is used to mean a battery, which is a device that is used to power devices such as clocks, torches, cell phones, etc. These cells are based on chemical reactions, which may or not be reversible. For reversible reactions, electricity has to be supplied to recharge the cell. If reactions are one way reactions, cells can only be used one time and once they are discharged, they cannot be reused.
There can also be other usages of cell, such as the box in which we add values in Microsoft Excel program, etc.
Hope this helps.