Since salivation in any animal is a reflex, Pavlov decided to probe deeper into the conditioning of the dogs. This later became known as classical conditioning. I have heard about Pavlov's dogs. Pavlov's study is also known as Pavlovian conditioning. This study is one of the most used studies in classical conditioning.
Conditioning is a type of learning.
Basically, what this study proved was that the dogs became conditioned by Pavlov to have expectations. After he noticed that the meat powder had this effect, he decided to try a different neutral stimulus. A neutral stimulus is something that normally would not produce any salivation. Pavlov chose to ring a bell since ringing a bell would not normally produce salivation in the dogs. Each and every time that the bell was rung, meat powder or food was given to the dog.