YouTube algorithm
Also called: the algorithm, YT algorithm
There is no single algorithm. YouTube runs separate ranking systems for the home feed, for search, for the Shorts feed and for suggested videos, and each one starts from a viewer and goes looking for something to put in front of them. The behaviour underneath is closer to automated word of mouth. When the system reads that someone enjoyed a video, it offers that video to viewers with similar taste, and a rejection pulls it back from those same people.
Two things creators get wrong. Every upload is judged on how it performs with the people watching now, so a channel's past success does not carry forward to the next one. And the system follows what your own audience already watches, which collapses pleasing the algorithm into pleasing the people you have.