What is "proto-malayo-polynesian"

The Proto-Malayo-Polynesian language (PMP) is the reconstructed ancestor of the Malayo-Polynesian languages, which is by far the largest branch (by current speakers) of the Austronesian language family. Proto-Malayo-Polynesian is by definition ancestral to all (certain) Austronesian languages spoken outside Taiwan, and Yami language off Taiwan's Orchid Island. Tai–Kadai languages are hypothesized to be a branch of Austronesian (but not Malayo-Polynesian), further scientific investigation is necessary to determine the relationship. (see Austro-Tai languages).