What is the difference between Add vs Attach vs Update in detached scenarios?

These methods define how the ChangeTracker treats an untracked entity graph (e.g., data coming from an API request).

Add() marks the entire graph (parent and children) as 'Added' (INSERT). Attach() marks the entire graph as 'Unchanged' (no DB update) unless property changes are detected manually. Update() marks the entire graph as 'Modified' (UPDATE), forcing EF to overwrite every column in the DB, even if unchanged.