What exactly is a kickback (in financial terms)? Is it kind of like a rebate or bonus gift?

Say for example that you are in charge of buying supplies for your company and three vendors bid to provide these supplies. Vendor A offers the pay you directly cash equally 10% of the value of the account, Vendor B offers 5%, while Vendor C offers nothing except the lowest prices. You choose Vendor A because the offer you the largest kickback (money that goes directly into your pocket).