When a ball is thrown vertically into the air, its velocity will become zero at the highest point of its trajectory. This point is known as the maximum height or the apex of the ball's motion.
At the maximum height, the ball reaches its peak vertical displacement and momentarily comes to a stop before reversing its direction and starting to fall back down due to the force of gravity. At this point, the velocity of the ball changes from positive (upward) to zero, indicating the transition from upward motion to downward motion.