For 'ADSL' broadband (the 'up to 8Mbit' you currently get on the Ledaig exchange) this means the distance between your house and the telephone exchange, which for some properties is many kilometers.
You can see the effect of distance on possible speeds here
In "superfast fibre broadband" ("VDSL2 Profile 17a") the telecom company's equipment ("DSLAM") is moved from the exchange into a new streetside cabinet, and a fibre optic cable links this cabinet back to the exchange (or even back to a different exchange altogether). This way, the length of copper wire is greatly reduced, and speeds can be increased.
The copper telephone line from your house to the nearest green cabinet in the street remains as it is.
A new cabinet is installed in the street, and a short jumper wire bridges your telephone line to this new cabinet.
How fast could this be? Depends on the distance of copper wire between your house and the nearest FTTC Cabinet.
Here is a table of speed vs distance for superfast broadband