Non-exclusive licenses (also known as beat leases or leasing rights) have restrictions in number of allowed sales units, earnings, etc., and can be sold to multiple artists at the same time. Elijah Melo retains full ownership of the beats when these licenses are purchased.
Exclusive rights allows unlimited use of the song you make with it on any medium without any limit on sales, streams, etc! After an exclusive rights license has been sold, that beat will no longer be available for any type of licensing in the future. If you buy exclusive rights to a beat, you become the owner of the beat.