Brakes
The brakes stop the vehicle - that is their only job, and everything else about them follows from it.
The foot brake works on all wheels. The HAND BRAKE is for holding a stationary vehicle. Pulling the hand brake at speed is dangerous: it acts on the rear wheels only and can put the vehicle into a skid.
Brakes need to be checked, not assumed. Check the brake oil level, and treat a soft or long-travelling pedal as a fault to fix before the next journey.
Brakes fade when they get hot, which is why a long descent is taken in a low gear rather than on the pedal. The most dangerous place for a brake failure is a road going downhill.
Your brake lights tell the driver behind you are slowing. A failed brake light removes their warning.