A cell is the basic structural and functional unit of life containing genetic material and organelles with specific functions and enclosed in a cell membrane.

Basic structural unit implies that every organism, no matter how big or small is composed of cells. Every human or even the 'giant​​' elephant to the smallest ant is actually comprised of cells.

Basic functional implies all life functions or characteristics observed in larger organisms are mirrored by or from a cell.

Cells can be classified into either plant or animal cells as well as either prokaryotic or eukaryotic cells. Check out out notes on cytology for more details.