A social media algorithm is the set of models a platform uses to rank content for each individual, predicting how likely you are to engage with, watch, or value a given post. It weighs signals like recency, relationship to the poster, content type, watch time, early engagement, and the topics you tend to interact with.
It matters because organic reach is not a queue — distribution is earned. The algorithm decides whether a post is shown to a few dozen people or a few hundred thousand, largely based on how the first viewers respond in the first minutes and hours.
You cannot game a modern ranking system reliably, but you can feed it good signals: make content people watch to the end, reply to, save and share; be consistent so the system learns your account; and match the format the platform is currently promoting. Chasing tricks ages badly; making genuinely engaging content does not.