Positive reinforcement
Adding something the animal wants immediately after a behaviour, so the behaviour happens more often — the R+ of training, and a technical term rather than a synonym for kindness.
The terminology comes from learning theory, where positive means added and reinforcement means the behaviour increases. So a treat delivered the instant a dog sits is positive reinforcement; a treat delivered thirty seconds later reinforces whatever the dog was doing thirty seconds later, which is usually standing up.
Timing and value are what separate it from bribery. The marker has to land inside about a second, and the reward has to be worth more to the animal than whatever it was going to do instead. This is the approach veterinary behaviour bodies recommend as first-line, and it works on cats, who are widely and wrongly assumed to be untrainable.