What kind of reinforcement is one that satisfies a biological need?

Primary reinforcement is generally the reinforcement that satisfies a biological need. They are natural and not learned. To illustrate, if you are thirsty and someone says that there is a glass of water in the refrigerator, there's a good chance that you'd walk there. If you weren't thirsty, however, the probability that you'd walk to the refrigerator is much less.

A secondary or conditional reinforcer is something associated with a primary reinforcer. For instance, money is not food, clothing, nor shelter, but it can be exchanged for such things.