There are sensors in the wheels that have batteries sealed in them. When you get new tires, it’s probably a good time to have the sensors replaces because when the battery goes dead, the car can’t read the sensor and the silly light comes on.
as far as the tire pressure in the tires, what the guy said is correct, but it’s only half of what you need to know. As a vehicle owner, the tire pressure should be manually checked monthly, and air added as needed. (Most people don’t do this, but should). That way you have a better knowledge of your tire pressure.