This data is from Ofcom, a snapshot of May 2018. According to Ofcom, this is what they represent;
SFBB availability (% premises) – Percentage of premises that have Superfast Broadband (30Mbit/s to less than 300Mbit/s) coverage
UFBB availability (% premises) – Percentage of premises that have Ultrafast Broadband (300Mbit/s or greater) coverage
Full Fibre availability (% premises) – Percentage of premises that have coverage from a full fibre service
% of premises unable to receive 2Mbit/s – Percentage of premises that do not have access to services above2Mbit/s
% of premises unable to receive 5Mbit/s – Percentage of premises that do not have access to services above 5Mbit/s
% of premises unable to receive 10Mbit/s – Percentage of premises that do not have access to services above 10Mbit/s
You can read more about it here.