Self driving cars use many different things to move around safely. Self driving cars are mounted with cameras, lidars (Light detention and ranging), machine learning, maps, and radars. The cameras are used to detect things around the car such as lane lines, speed signs, and traffic lights. Lidars are the spinning thing you may have seen on autonomous cars. It uses something similar to ecolocation but with lasers to make a map. Cars also have radars that find objects around the car and use maps and machine learning.
The first "autonomous car" was made in 1961 but every meter it moved took around 15 minutes. In March 2018, a autonomous car struck and killed a woman. This caused people to become wary of autonomous cars and question if they are actually safe too be used in public. There were also cars that allowed drivers to take their hand off the wheel. In November 2018, they made cars that are able to change lanes and leave freeways. Autonomous cars are meant to be drivejn on their own but the driver must still be alert if something goes wrong.
In 2004, DARPA created a competition for anyone to join. They had to create an autonomous car and make it strong enough to drive across the Mojave Desert. The entire race was 142 miles long and the farthest the best car went was a mere 7 miles. Despite the meager distance, they were determined and in the following year, 5 cars managed to make it to the end of the race. In 2007, they changed it to an urban challenge and they had to follow traffic rules and be safe. In 2009, the managed to even make a car that can drive on California's toughest road and a few years later, Elon Musk announced that he was making a self driving car.