The main difference between fibre broadband and an Asymmetric Digital Subscriber Line (ADSL), is that fibre broadband is faster.
ADSL broadband uses the old copper phone line network, while fibre broadband uses fibre optic cables, which either run to a street cabinet or directly to your household. These fibre optic cables allow for download speeds that are much faster than the copper ones used by ADSL.
Fibre broadband is also more reliable than ADSL and has a lower carbon footprint.