What is a kickback?
A kickback is an illegal payment to someone for preferential treatment. That payment can come in the form of cash, but it can also be valuable gifts or even financial favors, such as paying someone's mortgage. It can be considered a kickback if anything of value is exchanged for special treatment.
There is always some sort of collusion at the root of a kickback, which can involve outright fraud or simply steering customers toward a particular company, investment, or fund. Kickbacks are highly illegal, so everything that flows from them can be considered to have corrupt intentions.