A memo or memorandum is a type of communication commonly used in businesses. Memo's are sent to colleagues and co-workers. A memo is used as a written reminder or to convey a short proposal or some basic information. A memo format is generally short consisting of between one and four sentences. A longer format might consist of several paragraphs but should never exceed one page in length. If the information you need to communicate exceeds one page it is probably better to write a report.