What is ethylene rubber (EPDM)?

Ethylene rubber is short for ethylene-propylene-diene rubber. It is a
synthetic rubber
i.e. made from petroleum and natural gas components.

The main use of EPDM is in seals / O-rings and hoses. EPDM is highly resistant to weather, oxygen and ozone, has good rebound resilience and can withstand higher temperatures than natural rubber.
natural rubber
and is resistant to many chemicals. However, they do not adhere well to metals or textiles.