What is biking?
biking is when you ride a bicycle
Mountain biking is a subset of cycling, like off-roading with a jeep is another type of car driving. From a riders perspective (XC) mountain biking is more dynamic, more out-of-the-saddle work with bigger changes in pace. Road biking is more about endurance and slogging it out mile after mile. Then there are the subsets of MTBing, like downhill, which is a phenomena all to itself.