Where Obsidian keeps files, Notion keeps a hosted database: every page is a stack of blocks, and a database row is itself a page. That makes it good at structure — a projects table with a status property, a reading list as a gallery — and weaker at leaving, since an export is a snapshot rather than the source.
PARA and GTD setups are common in it, built as linked databases: projects, areas and next actions as rows that point at one another.