To understand how forks work, it’s important to first understand the participants involved in the decision-making process (or governance) of the network.
In Bitcoin, you could broadly make the distinction between three subsets of participants – developers, miners, and full node users. These are the parties that actually contribute to the network. Light nodes (i.e., the wallets on your phones, laptops, etc.) are used extensively, but they aren’t really “participants” as far as the network is concerned.