A brief answer,
Insulators are mainly for insulation, and their function is to support wires and increase creepage distances; the picture is as follows (the part connecting the tower and wires on the way is the insulator, used It is a glass and composite suspension product):
Lightning arrester is mainly a device that protects the substation equipment from lightning shock waves
If you want to explain it carefully, it will take a lot of space. I hope you can understand from the two pictures.