YouTube algorithm
Definition
The recommendation system that decides which videos to show, primarily driven by click-through rate and watch time.
The YouTube algorithm is the recommendation system behind Search, Suggested and Browse. It is not one thing — it is a set of models predicting what each viewer will click and keep watching.
In practice two signals dominate: click-through rate (your packaging earns the click) and watch time / retention (the video keeps the promise). Optimize those and the algorithm does the distribution. Chasing it any other way is wasted effort.