My guess is that 75% of the world's cyclists have never really paid much attention to their pedals.
So long as they spin round, push the crankset in the right direction, and give you somewhere to rest your feet, they are of little interest.
Remember your first bike? Maybe you do, but you could probably not tell me what the pedals were made of, what weight they were, how much they cost, what cleat system they used, or how easy they were to service.!!
However, as bikes have become more complicated, and folk have more money to spend on personalizing them, the pedals have attracted more attention.
Here is a good example - the Shimano A530 SPD's.

Shimano are one of life's fascinating mixtures. I had been aware of the firm's fishing products for quite a long time. They have pioneered new technology and introduced it at the entry levels to their ranges. Many firms work the other way around - introducing the innovation at the most expensive level, and once it has paid for itself, the plebs can enjoy it later on.
In fact Mr Shimano started his career with a bicycle interest, having a special passion for freewheels and derailleurs.
By the time the firm took up their fishing tackle side, they already had the biggest bicycle factory in the world.
They have ventured into snowboarding and golf equipment as well, and are clearly concerned to provide good equipment through which folk can enjoy the outside world.
In the world of cycling, they have introduced loads of ideas and technology at every level.
If you watch any professional cycle race, these days, you'll spot Shimano products all over the place.
2 The Concept
^^^^^^^^^^^
The first cleats were introduced to cycling before Mr Shimano was born.
The concept was fairly simple.
If you pedal along really fast and your foot slips off the pedal, you risk injury to a muscle or even a tumble off your bike.
One solution was a clip or strap into which you place your foot to keep it in place. Straps are difficult to get your foot into, and giving yourself a helping hand while on the move, can be even more risky than your foot coming off the pedal.!
The cleat was a further progression then. You have a shoe with a metal cleat screwed to the sole. This clips into a mechanism on the pedal and locks your foot to the pedal.
Early models needed a hand to lock them in place with a lever! .. somewhat dangerous, methinks.!
Modern ones worked much more simply with a quick forward movement of the foot to lock the cleat into the mechanism, and an outward movement of the heel to release it.
The problem tackled by Shimano in the late 1980's, was how to have a shoe with a cleat bolted to the sole, which could also allow the owner to walk on the path !?
The firm's solution is a smaller cleat which is bolted to a recess in the shoe and acts as part of the shoe tread when walking rather than cycling.
So was invented the SPD - the Shimano Pedalling Dynamics - worth explaining because SPD can stand for all sorts of other things too.!

4 The Experience
^^^^^^^^^^^^^^^
I had used the cleat system on a static bike in the gym, but was a bit apprehensive about the experience out on the open road.
Fitting the pedals took about ten minutes, and I tried using them in the privacy of the back yard first.
The cleats engaged very simply - just a tiny push forward with the foot - and released very easily too. This is important as failure to release when needed spells disaster. Imagine you have just arrived at traffic lights in rush hour. You have either forgotten to release your foot, or failed to be able to because the release mechanism was too stiff. You have braked and reached a halt, but neither foot is free to put on the ground. The inevitable is inevitable. You fall to the ground, with bike on top of you, your feet still firmly locked in place. Every bike-hating driver in sight is rolling about in laughter. Every sensitive citizen is rushing to your aid, convinced that either a car knocked you over, or you are in the throes of a heart attack. Police and paramedics have been phoned to cover either eventuality, and you are struggling with massively hurt pride and total inability to free your feet from the cleat mechanism.!
I had also worried about the ease - or lack of it - of getting the correct side of the pedal where I needed it while on the move. So far, this has not been difficult. The pedals seem to be so well balanced that a quick flick of the foot gets everything in place.
There is no doubt that this system transfers all one's energy into forward motion, keeps the feet in a safe position, and generates more speed as both the upward and downward movement of the legs is productive.