In the image above, what is the round button the yellow arrow is pointing to? (You can click on the image to enlarge it).

Yes, it is the starter button

Chrysler was the first to replace the floor-mounted starter button with a key starter switch on the dashboard in 1949. Others followed suite. The key starter remained the only way to start a car until 1998, when Mercedes-Benz introduced “Keyless Go” on the S-Class. Keyless entry allows drivers to once again push a button to start their car.

Not old enough to know this?

It is the starter button. Electric starters were introduced on the 1912 Cadillac. By 1915, 98 percent of production cars used the system, with the exception of Ford. The starter buttons were mounted on the instrument panel or floorboard until 1949, when Chrysler replaced the starter button with a key starter switch.

https://www.hagerty.com/media/people/push-button-start/