5 Star Service
An API - Application Programming Interface - is an interface through which interactions can happen between various software components. In general terms it’s a set of clearly defined methods of communication that different ecosystems can use to integrate with each other.
Most Home Automation controllers provide a Local API to enable the development of services and applications used to integrate products. Similar to a Cloud API, one can extend functionality by writing own software code to interact with third-party devices / controllers via its Local API meaning faster response times and no need for an internet connection.