It´s hard to explain to me in English ... but I could try.
This code belongs to a coordinator in a 802.15.4 network. It recolects the information of its remote nodes.
This information as you can see it treated by two functions, first it listens (readRequest) if there is a frame it save the information in the microSD as a file (generateJson).
Besides, It listens to incoming request from the internet, there are only 3 GET /HTTP1.1. GET /fioList HTTP1.1 and POST /changes. So as you can see there are functions that answer to them.
The microSD have as files as remote nodes are, and the html code of the webpage in html. So when you receive a GET /HTTP1.1 The board print to the client the page that reads from the microSD card.
The same when a GET /fioList arrives ....
and when a POST message arrives the coordinator just pick up the two variables and send to nodes or save it for doing later.
Please ask me everything you don´t get. I know ... this is too much ... sorry and thank you.