Things You Should Know Before Using ESP8266 WiFi Module
ESP8266 Pinout, Datasheet, Features & Applications - The Engineering Projects
Getting Started with ESP-NOW (ESP8266 NodeMCU with Arduino IDE)
ESP8266 Client-Server Wi-Fi Communication Between Two Boards (NodeMCU)
Using the ESP8266 WiFi Module with Arduino Uno publishing to ThingSpeak, by Christopher Grant
Getting started with NodeMCU (ESP8266 tutorial #1)
ESP8266 Pinout Reference: How To Use ESP8266 GPIO Pins
ESP8266 NodeMCU Access Point (AP) for Web Server
ESP8266 Wi-Fi Module Datasheet : Working & Its Applications
NodeMCU ESP8266 Specifications, Overview and Setting Up
Using the ESP8266 WiFi Module with Arduino Uno publishing to ThingSpeak, by Christopher Grant
Building Smart Drones with ESP8266 and Arduino