BlynkSimpleEsp8266.h library

What is the function of BlynkSimpleEsp8266.h library?
I know that I need it if I’m using NodeMCU with Blynk I want to know what does it do?
There is “ESP8266WiFi.h” for including ESP8266WiFi and “Blynk.h” for including blynk library, but what exactly “BlynkSimpleEsp8266.h” used for?

it creates the Blynk singelton object over the esp8266 WiFi library