If your mom wants you to mow the lawn but you don't feel like it, she might offer to treat you to ice cream after as an incentive. An incentive is something that stimulates you to take action or work harder.
This noun dates back to Middle English, from Late Latin incentivum, from incentivus, "stimulating." In Latin, incentivus meant "setting the tune," from incinere, "to sing." The related English verb is incentivize. The less common verb incent was first used in the early 1980s, and has been criticized as business jargon.