They work in the same way that household refrigerators do, they use an insulated airtight compartment to absorb heat and dissolve that heat outside the compartment to ensure the inside contents stay cool.
Almost all types of Refrigerated trucks, with and without drivers who have done a CDL training course, are available for hire on a short-term, long-term, day-to-day, week-to-week, month-to-month, and yearly basis, as well as for trips and events.