Explanation/Reference:
Explanation:
Sharing With Authenticated External Users
Content can be shared with authenticated external users, meaning guest users are sent an invitation by email and prompted to sign in using an account from a trusted provider in order to access the content in question.
Once the invitation is accepted, they are added to your organization's directory as an external user, but will only have access to the specific elements you shared with them. If you've shared an entire site, they'll have access to everything in it, so make sure it doesn't contain sensitive content.
References: https://en.share-gate.com/blog/ultimate-guide-deal-with-office-365-external-sharing