what is continuously varieable auto transmission

A continuously variable transmission or CVT does not have set gear ratios like a traditional 3 or 4 speed transmission. Most CVT transmissions use two cone shaped drums above one another. There is a chain connecting the two drums together. This chain will slide back and forth across the cones varying the gear ratio. For example the engine driven gear will start on the narrow end of the cone while the output cone is on the fat end. This creates gear reduction for power to start the vehicle in motion. As the vehicle increases in speed the chain slides until the chain is on the fat side of the engine driven cone and the narrow end of the output cone. This creates an overdrive ratio for higher speeds. The main advantage is fuel economy. The gasoline engine can stay at a constant rpm where it is most fuel efficient while the transmission can increase the vehicle speed. Search the internet for a visual model of a CVT and it will make better sense.