|Common Gateway Interface (CGI)||An interface specification for web servers to execute programs like console applications running on a server that generates web pages dynamically. In brief, an HTTP GET or POST request from the client may send HTML form data to the CGI program via standard input.|
|Application program interface (API)||A set of routines, protocols, and tools for building software applications. Basically, an API specifies how software components should interact. Additionally, APIs are used when programming graphical user interface (GUI) components.|
You may refer to this article to see the model of Reolink device that supports CGI/RTSP/ONVIF: Which Reolink Products Support CGI_RTSP_ONVIF
The PDF attached in this article shows the CGI/API command that Reolink supports.