Protect / Identity Management, Authentication, and Access Control
Identity assertions are protected, conveyed, and verified.
Think of it likeWhen a neighbor texts to vouch that the repairman at your door is legit, you confirm the text really came from the neighbor and was not faked before you trust it.
In plain English
When someone else vouches for a visitor, the family makes sure that vouching message is genuine and untampered before acting on it.