"That front page" isn't the front page, it's the release notes for version 7.0.0.

The actual front page has "The Package Manager for Everywhere" as its subtitle (and that exact description as part of its <title>), and that is basically all you need to know. It's a staple for Unix-y power users on macOS (but supports Linux too, including WSL), and version 1.0 will be ten years old next week. You're not very far off from complaining that Postgres release notes don't explain that Postgres is a database.