Pedals. You have three choices of pedals: platforms, toe clips and clipless pedals.
Since your feet aren’t attached to simple platform pedals, they don’t allow you to maximize your stroke; all you can do is push down, but not pull up.
Toe clips (also known as “toe cages”) allow you to use more of the pedal stroke. The drawback is they need to be snug, which makes them harder to pull out of for quick stops.
Clipless pedals, which attach directly to a cleat in the bottom of your shoe, take a little getting used to, but with practice you’ll be able to get in and out of them in a snap, as well as get the most out of your pedal stroke.