They contained their essential components inside a cell wall and a membrane that allowed necessary chemicals to come in and wastes to go out. They were able to select the chemicals that they needed to live. They could reproduce themselves by simple cell division. There are still many procaryotes on earth today. Procaryotes released oxygen into our atmosphere.
Eucaryotes are cells that have their DNA in a nucleus inside the cell.
They are larger and more complex than procaryotes. All the multicellular life forms on earth have cells with nuclei. The early development of life was very slow, as can be seen from this chart. Procaryotes were the only life forms on earth for longer than all other living organisms have existed, and they are still here. Mammals have been here only a very short time in comparison.