Fibre Broadband = Faster speed
Fibre to the Cabinet is the official name. It means that from the internet itself right to the local green box on your street or nearest your premises has a fibre connection and no longer relies on copper wires to bring the broadband signal over.
No longer can heavy rain, electromagnetic interference from a faulty car alarm etc. degrade your service.
The final part of the journey will still be delivered over a copper line so the service depends on how far away you are from the local green box.