Shimano and its SPD or Shimano Pedaling Dynamics system took the world by storm, and ever since the far majority of cyclists in every conceivable discipline uses it or some variant.
Although the term “clipless pedal” is somewhat confusing, it harkens back to the day when toe-clips where attached to pedals for the benefit of being able to pull the pedal upwards as well. The removal of the toe-clip turns the pedal into a clipless version, hence the name.
The reason for clipless pedals over traditional flat pedals or pedals with toe-clips are numerous and deserve its own article. The core reason for clipless pedals is its unparalleled ability to maximise the energy transfer into the pedal stroke, without adding a lot of weight to the pedal itself (and the shoes if you count the cleats).
Very quickly many types of pedals have been created such as road bike clipless pedals, and of course clipless pedals for various mountain bike disciplines such as XC clipless pedals, trail and enduro clipless pedals, and pedals meant for downhill racing. Whatever style you’re looking for, you’ll find specific articles with in-depth information right here.