In an exclusive lease license, the parties agree that no other person/legal entity can use the instrumental, except the licensee.
On the other hand, a Non-Exclusive License grants to the licensee the right to use the instrumental, but on a non-exclusive basis. That means that the licensor can still sell the same instrumental and they can also allow other licensees to use the same beat.
Their licensing details are always defined by the individual producer/beatmaker(licensor).