Letters are used to formally inform the UN community of events and the outcome of non-UN meetings, to transmit reports or communications, and for a variety of other purposes.
It is possible to search for many of the Secretary-General's letters using the UNBISnet.
A letter sent by a Member States usually specifies the body to which it is addressed and may specify the agenda item(s) under which it is submitted. Letters submitted by Member States can be retrieved using the UNBISnet.
Consult the following section of the UN Documentation Research Guide: