the meaning for OS API

[shadowkane]

Hello,
I have something i didn't understand, to be more specific i can't get the meaning of "The main task calls OS API to create the application task.", what is this 'OS API'.
i'm reading the documentation of ESP32 for the wifi section and in the general scenario of the wifi station in the init phase, " create app task", as i understand, it's the task where i call the wifi APIs to create and init the others tasks (like event task and tcp/ip adapter task ).
well i can use the app_main task or create another task that create and init those tasks and call it from the app_main task. is that what it mean by the main task calls OS API to create the application task?