MaaP, Messaging as a Platform, is the GSMA's name for the business layer of RCS: the platform that lets a brand run a chatbot or interactive service inside the phone's native messaging app, with rich cards, carousels, suggested replies and tappable actions, rather than through a separate app. Google's RCS Business Messaging is the MaaP implementation most US carriers use.
What the platform does
A MaaP platform sits between the business and the carrier's RCS network. It hosts the agent, holds the verified identity, exposes an API for sending rich messages and receiving replies, handles capability checks and fallback, and reports delivery and read events back. Without it, RCS would only be a richer way for two people to text; with it, the inbox becomes a place a business can sell, support and confirm.
How it relates to RBM
The Universal Profile specifies MaaP; Google Jibe and RBM are Google's hosted version of it, which is why the two terms are often used as if they were the same. On a carrier that runs its own RCS infrastructure, the MaaP platform may be the carrier's own or a partner's, and a business reaches it through an aggregator.
In practice
A brand does not build on MaaP directly. It works through a provider that is connected to the platform, files the agent for verification, and sends through that provider's API or app. What is an RCS chatbot covers what gets built on top.