The ball is very similar to a tennis ball. The size and weight of the ball is almost the same. The main difference between padel and tennis balls is that a padel ball has less pressure than a tennis ball. So that means that when the ball bounces, it bounces a little bit lower.
You can play with tennis balls. Sometimes beginners play with tennis balls, and that’s OK. But if more advanced players play with a tennis ball, because the ball has more pressure and bounces higher, it’s easier to hit the ball out of the court. When you smash it, the ball bounces more and goes over the glass more easily than with a padel ball.
Also, because the bounce is a little bit lower and slower with a padel ball, it gives you more chance to play longer points because you have more time for positioning.