Why do brakes jam and the brake pedal becomes stiff?

Brakes can jam and the brake pedal can become stiff due to several reasons, including air trapped in the brake lines, a malfunctioning brake booster, or a seized caliper. When air is present, it can prevent proper hydraulic pressure from building, affecting pedal feel. A faulty brake booster can inhibit the assist necessary for smooth braking, while a seized caliper can cause the brake pads to remain engaged. Regular maintenance can help prevent these issues.