A good ball handler is able to dribble smoothly and quickly. It's important to not lose control of the ball while dribbling it, and to be productive with the ball. This means getting around defenders, finding openings to pass or shoot, and not turning the ball over.
The NBA is filled with great ball handlers. Ball handling alone is enough to make a player very valuable to a team, as a good ball handler can drive the ball up the court. Kyrie Irving is often pointed to as the best ball handler in the NBA, with Steph Curry and Kemba Walker also being a part of the conversation.
Since ball handling is the basic control and movement of the ball, bad ball handling damages a player's ability to possess the ball. Poor ball handling leads to big problems: