All chainsaws have either manual or automatic pumps that dispense oil evenly on the saw chain. The oil removes friction and help the chain slide easily around the bar. A well lubricated saw chain should be able to cut well with no problems at all.
If the bar and the chain are not well lubricated, the friction caused when the chainsaw is being used to cut wood can cause the bar to overheat.This will damage both the chain and the guide bar. Overheating can also cause irreversible damage to the engine.