We have two options available for end stops: optical and mechanical. Mechanical uses a switch, which triggers when hit. The optical uses infrared and detects a blockage of the light with a sensor. The advantage of a mechanical end stop is the easy implementation, the optical end stop can be a bit fiddly. But the mechanical end stop has a much shorter lifespan, as it wears out sooner. Another advantage of the optical end stops is precision, especially for the Z-axis a high precision is recommended.