An ADSL connection gives you broadband via the old copper phone line network to your home. With ADSL you can expect an average download speed of about 10 Mbps and average upload speeds of 1 Mbps. This is ok for emailing, surfing the web and checking social media, but is not the best experience for streaming media i.e. Netflix.
A VDSL connection also uses the copper line but offers faster speeds than ADSL. Please note, this connection may not be available to everyone. VDSL will give you download speeds of up to 50 Mbps and upload speeds up to 10 Mbps (again noting that these are the theoretical maximum speeds available, and average speeds will vary). VDSL improves speed over short distances, but you will need to be located within 800m of the relevant cabinet or exchange to take advantage of speeds up to 20 Mbps or more.
The speed for ADSL and VDSL is dependent upon distance and the neighbouring traffic.