Pedals, by Bob.
I’ve been asked about pedals by members who haven't yet made the ’big step’ to clipless. Yes, there are several different systems, but there are just two basic styles:
There’s the ones where the shoe plates stick out and make you waddle like a duck when off the bike such as Look, Time, Speedplay, SPD-L etc.
And then there’s SPDs, where the shoe plates are recessed and you can walk like a human being. SPDs are probably what you already have on your mountain bike if you use plates. SPDs are not seen as sexy, because they are not used in the peloton. In SPDs, there are Shimano ‘Mxxx’ types (double sided) and ‘Axxx’ types (single-sided).
This article from The Comic explains the different systems.
It is said that if you are a powerful rider, you may find that SPDs can be uncomfortable for long distances, but I’ve found them OK up to a ride of 300 miles. However, I did use ‘Look’ for racing.
[Ed. I have SPDs on my mountain bike as Bob suggests but on my road bike I switched to Time as they have more "float", meaning angular rotation, which is supposed to help your knees. My knees stopped aching after that - it may have been the pedals. Anyway, I waddle like the ducks and the pros now.]