> I watched an hourlong introduction video and could still barely grasp it

I can relate to that. What helped me to understand it though is looking through some projects using Salsa [1] and reading the document about how the Rust compiler uses queries [2]. You might also want to watch the discussion video with Anders Hejlsberg [3] that gives an overview of the problems that Adapton/Salsa try to solve.

[1] https://crates.io/crates/salsa/reverse_dependencies

[2] https://rustc-dev-guide.rust-lang.org/query.html

[3] https://learn.microsoft.com/en-gb/shows/seth-juarez/anders-h...