In the world of tennis, there are primarily two types of balls: pressurized and pressureless. Pressurized balls are the most common and are used in professional matches. They have a hollow core filled with air, offering a good bounce, speed, and spin. On the other hand, pressureless balls are solid inside and are ideal for beginners or for use in practice sessions because they last longer but don't bounce as high. So depending on your level and purpose, you can select the tennis ball that suits you best.