Difference:
1, "Request for Instructions" is used to request the approval of "superior".
2. The "letter" is a request for the approval of the "relevant competent department".
In practice, it often happens that the organ that needs approval is not the "immediate" superior of the organ, but the "collateral" superior.
Extended data:
The main features of this letter are:
communicative
Letters play a communication role in negotiation and question-and-answer between different subordinate organs, which fully shows the function of parallel language, which is a feature that other official documents do not have.
flexibility
Shown in two aspects.
1, flexible writing relationship. Letters are parallel official documents, but they can be written up or down in addition to parallel writing, and there are no strict restrictions on special writing relationships like other languages.
2. The format is flexible. Except that the main letter of a senior state organ must be written in accordance with the format and writing requirements of the official document, other general letters are flexible and can be handled in accordance with the format and writing requirements of the official document. You can have a home page, or you can have no home page, and you don't have to make a document number or even a title.
simple
The main content of a letter should be single, and a letter should only write one item.
Baidu encyclopedia-letter