What do you mean by anonymous

Anonymous means 'unknown', It can refer to a person, place writer, or anything whose origin is unknown

When you talk about anonymous, it can be a person, a place, a thing, or an event. Anonymous means that you do not know anything about the object of reference. Its an adjective to describe information that is witheld or is chosen not to be shared.

Examples of this is when it is used in the sentence "That letter came from an anonymous author.", the person does not know who wrote the letter or why it has been sent in the first place.