The ball is in your court
Phrases like these are used because they provide an easy way to quickly communicate an idea. The phrase ‘The ball is in your court’ is a commonly used idiom in the English language.
Most people are familiar with the sport of tennis, so in tennis if the ball is in your court then it is your turn to hit the ball to continue the game.
While the phrase ‘the ball is in your court’ does indeed describe a play in the game of tennis, this is not the intended meaning when used in casual conversation.
It actually refers to the decision making process in which another person has the responsibility to make the next action or make the next decision.
For example – ‘I offered Jenny the job. It is up to her now. The ball is in her court.’