A quote from Microsoft's M language specification:
The Microsoft code name "M" Modeling Language, hereinafter referred to as M, is a language for modeling domains using text. A domain is any collection of related concepts or objects. Modeling domain consists of selecting certain characteristics to include in the model and implicitly excluding others deemed irrelevant. Modeling using text has some advantages and disadvantages over modeling using other media such as diagrams or clay. A goal of the M language is to exploit these advantages and mitigate the disadvantages.
