Instead of charging interest for lending, the lender pays the borrower interest on the amount.
But, why would someone need to do that and when does it make sense to do that?
This is nothing new and was first known to take place post the 2008 subprime crisis or the great recession.
On 2 July 2009, Sweden’s Riksbank was the first central bank in the world to introduce a negative interest rate, when it brought its repo rate (the rate at which a central bank lends short-term money to commercial banks against securities) down to 0.25%. This caused the deposit rate (the interest commercial banks get for depositing money with the central bank overnight) to go down to −0.25%, while the overnight lending rate (the interest a central bank charges commercial banks for overnight lending) was pushed down to 0.75%
Source : “Repo rate cut to 0.25 per cent” (PDF) (Press release). Sveriges Riksbank. 2 July 2009. Retrieved 1 August 2018.