as salam alaikum
interest has been defined as "money paid at a particular rate for the use of money lent". It is one type of usury (riba) and it should be avoided.
Another type of usury/riba is an "exchange of the same good by unequal quantities or qualities" that some may still define as a form of interest but technically and according to common view has not been considered as such.
With prayers for your success.