What do they actually do? With any wiring work undertaken on a property, you will find a circuit breaker. If any electrical wiring short circuits then without a breaker you are risking electrocution. Before it comes to this, the breaker will cut off all power to a faulty piece of equipment rendering it useless but is also completely safe until a problem has been fully rectified.
When applying circuit breakers, it can prove to be a very complex workload to an inexperienced d.i.y. hound so if your home does not have this essential element then contact a fully qualified electrician to safeguard your home against possible disasters.