In the past few decades, different balls in terms of pressure have been developed to adjust to different age groups, namely sponge, red, orange, and green balls.
This initiative has been great since it allows very young kids to be able to develop skills they would otherwise not be able to. Besides that, there are also three main types of balls when it comes to the regular yellow ones we all know.
Professional Tennis Balls: These are the premium, high quality balls meant to provide a great and consistent feeling. Professional tennis balls are meant to last a couple of matches at the high level. They also tend to lose their fuzz quite quickly in comparison.
Championship Tennis Balls: these are a step down from professional, in both pressure and felt quality, but also in price. This style is best suited for practice play and are designed to last longer than just a couple of matches.
Practice Tennis Balls: Practice or coach balls are harder and much denser balls, and not intended for official play and matches. Instead, they used are for practice and also great for ball machines since they can hold fuzz and pressure for much longer.