Surfing is a way of travelling along angled surfaces (known as ramps) fast, which in turn allows a new kind of gamestyle. Reach new heights. 'Surf maps' usually allow getting to places that normal-style playing would never allow, due to the rapid speed that can be built up.
If you want to try surfing, and hopefully, if you are a member, you will / have, then here are some good friendly servers.
#sbg-clan.com|TF:2|#01#|surf|instant respawn|hlstatsx.eu - 220.127.116.11:27015
#sbg-clan.com|TF:2|#02#|surf|instant respawn|hlstatsx.eu - 18.104.22.168:27015