Hi dadada, To put it simply and succinctly, "yet" means something which you have been anticipating has not happened up to the present moment. "yet" is often used with "to-infinitives" which express an element of anticipation. An example: I have yet to hear from the client. ("to hear": anticipation that the client would call / "yet": client has not called up till the present moment.) "yet" can often be used with "to + be + verb (past participle form)" An example: The murder weapon was yet to be found. In this case, the "murder weapon" is the object (or receiver of an action). The subject (or doer of an action) is sometimes omitted from a sentence (i.e. The murder weapon was yet to be found (by the police).) So, in your sentence, you are assuming that the listeners have prior knowledge of the contents of the letter; however, in reality, they have not read the letter (and have not received this knowledge) at the moment (i.e. yet to receive). *This makes sense. When we are introducing something for the first time, we use the indefinite article "a" because the reader does not have any prior knowledge of this thing. Subsequently, we can use the definite article "the" because both the reader and writer now have a common understanding of this thing. Example: "We are proud to announce the arrival of A new software. THE software will revolutionise the way we... I hope this helps you.

it means they have not received the information at this time (yet).

Hey dadada, how are you? The expression ''yet to receive'' just means that they have not received the information up to the present time. The usage of ''yet'', placed right after the verb ''have'', is a far more formal way to convey the aforesaid meaning than that where ''yet'' is usually put at the end of a clause. Please, have a look at the explanation below for a better understanding: 1) In EVERYDAY speech, you use ''yet'' in negative sentences to say that something has not happened up to the present time, although it probably will happen. In conversation and in less formal writing, you usually put ''yet'' at the end of a clause. E.g.: ''It isn't dark yet.'' E.g.: ''I haven't decided yet.'' E.g.: ''She hasn't arrived yet.'' 2) In FORMAL writing, you can put ''yet'' immediately after ''not''. E.g.: ''Computer technology has not yet reached its peak.'' E.g.: ''I presume he has not yet forgiven you.'' E.g.: ''They have not yet set a date for the election.'' *** As regards the FORMAL writing, instead of saying that something ''has not yet happened'', you can say that it ''has yet to happen.'' People often use this structure to show that they do not expect something to happen. E.g.: ''I have yet to meet a man I can trust.'' E.g.: ''Whether it will be a success has yet to be seen.'' E.g.: ''I have yet to receive the information.'' Hope that helps! Should you have any further questions, do not hesitate to contact me. I shall be pleased to help.