What is the difference between primary cells and cell lines?

Primary Cells versus Cell Lines

Primary cells or finite cells, are cells that are directly prepared from an organism’s tissue using enzymatic or mechanical methods. Under the right conditions, primary cells will grow and proliferate, however, they are only able to do so a finite number of times. Once that number is attained, cells enter a stage of senescence where they can no longer divide.

Cell lines are permanently established cell cultures that will proliferate indefinitely under the right conditions. Cell lines are preferably used for convenience as they are easier to handle and widely published, such as HeLa and HEK 293 cell lines.