There are two ways of licensing: Non-Exclusive and Exclusive.
There’s only one exclusive license, but you can offer and sell different non-exclusive licenses. For example, a Basic, Premium and Unlimited license. The Basic license would be the cheapest option. And the Unlimited license the most expensive.
You can sell non-exclusive licenses to an unlimited amount of artists. But an exclusive license can only be sold to one person.
Once someone purchases an exclusive license, other artists can no longer buy a license for that same beat. Generally, producers then mark the beat as ‘SOLD’. Or remove it entirely from their website after it’s sold ‘exclusively.’
Artists that have licensed the beat before the exclusive rights were sold are still allowed to use the beat for the length of the term in the license.