“Cyf.” Is short for “Cyfyngedig” and means “Limited” in the Welsh language, so, if it was an English company, “Burtech Cyf.” would be “Burtech Ltd.”
An un-braked trailer has no braking system at all. On the move it relies on the towing vehicle to retard it. When parked and disconnected from its towing vehicle it must be chocked or otherwise secured. The maximum gross weight that an un-braked trailer can be is 750kg, although lower restrictions may apply depending on the vehicle pulling it.
A braked trailer, most commonly, has an over-run braking system. As the towing vehicle slows, the trailer pushes onto the back of it. A mechanical connection from the coupling to the wheels causes brakes in the hubs to be applied, slowing the trailer down. You would expect that this action would cause the brakes to apply if the towing vehicle was to reverse, pushing on the trailer. A mechanism within the brakes allows the trailer to differentiate between the brakes being applied to slow the trailer when going forward and when is being reversed. This is known as “Auto- reverse brakes”.
When a braked trailer is parked and disconnected from its towing vehicle, a handbrake lever near the coupling is used to apply the brakes, removing the need for it to be secured in any other way.