How do bikes work?

Can you elaborate on the inner workings of bicycles and how they operate? Specifically, how do the pedals, gears, chain, and wheels all come together to create motion and allow for efficient transportation? Additionally, what are some of the key components that contribute to the overall performance and durability of a bicycle? I'm particularly interested in understanding the mechanics behind how the pedaling action is converted into forward movement and how the gears are adjusted to increase or decrease the level of resistance.