A "chartered jet" is a private airplane that is rented or leased. It allows people to have a plane all to themselves for their specific needs instead of traveling on a commercial airline with other passengers. Full definition
You might think private charter jets are only reserved for the rich and famous. (abackpackerstale.com)
As an aside, I am a pilot and I went to the airport this morning early, and watched some of the 70 charter jets take off and saw a few politicians departing. (inc.com)
Do a light charter jets comparison to find the aircraft that fits your needs, and then consider the price. (aswetravel.com)