Guys, can you tell me why some cars have 2 brake calipers? And also what is the use for vented brakes?

You must mean two brake calipers on the rear, the bigger caliper is you main brake and the smaller caliper is a parking brake, and vented rotors are for cooling down.

Most cars have 4 brake calipers, actually. Some cars have 2 because they have drum brakes in the rear.

Also, vented brakes are because track day bro… Keeps brakes cool to avoid brake fade