informazione xively

salve ,per favore qualcuno mi può spiegare questa parte di uno script cosa scrive?(stringa)
un file .csv oppure aggiorna solo un file .csv?
a cosa serve apikey?

 // this method makes a HTTP connection to the server and sends a STRING with
multiple readings
  if (client.connect(xivelySite, 80)){
    client.print("PUT /v2/feeds/");
    client.print(FEED_ID);
    client.println(".csv HTTP/1.1");
    client.print("Host: ");
    client.println(xivelySite);
    client.print("X-ApiKey: ");
    client.println(KEY);
    client.print("Content-Length: ");
    client.println(dataString.length());   // use String func to calculate the
length of the data sent

    // last pieces of the HTTP PUT request :
    client.println("Content-Type: text/csv");
    client.println("Connection: close");
    client.println();
    client.println(dataString);         // here's the actual content of the
PUT request:

edit by mod: per favore includi il codice usando gli appositi tag