What is the difference between facultative and treaty reinsurance?

With Facilitative Reinsurance, individual risks are offered by a ceding insurer for acceptance or rejection by the reinsurer. With Treaty Reinsurance, the reinsurer and ceding (or offering) insurer have agreed that a specified portion of the type or category of risk as specified in the reinsurance treaty will be ceded (or offered) by the insurer and accepted by the reinsurer. Fac covers an individual risk, treaty covers a group of risks.