Difference between allow write and allow create update in Firebase database rules

Question

Could anyone tell me what is the difference between allow write and allow create update in writing conditions for Cloud Firestore Security Rules?

Answer 1

This is covered in the documentation for granular operations.

write is exactly equivalent to the combination of create, update, and delete. If you allow write, you are implicitly allowing all three more specific permissions. If you allow only create and update, it does not allow documents to be deleted.