In cell biology, an organelle is a specialized sub-unit, usually within a cell, that has a specific function.

The most well-know are the cell nucleus (DNA sources), mitochondria (power plants),

cell membrane (separates contents of cell from outside), and Golgi apparatus (processes and modifies proteins). Many different organelles work together to keep the cells viable and healthy.

See the reference for a more detailed list and explanation of Eukaryotic cell organelles. No need to get too technical here.

More Info: en.wikipedia.org