To collaborate with someone using a Google Doc, what information do you need?

To collaborate with someone using a Google Doc, you need the person's email address because that is how Google Docs manages sharing and collaboration features. When you want to share a document, you typically enter the email address of the person you want to collaborate with, and they receive an invitation to access the document. This email identifies the user in the Google ecosystem and ensures that the correct permissions can be granted, whether it's view-only, commenting, or editing access.

While having a shareable link allows anyone with that link to access the document, it does not specifically facilitate targeted collaboration or permissions management like using an email address does. A Google account is also essential for collaboration, but simply having the account is not sufficient; you still need the email address for sharing. A phone number is irrelevant for accessing or collaborating on Google Docs.