Choose the firmware that interests you
ESP Easy is a firmware designed for ESP8266 modules which allows you to create connected objects without any programming. ESPEasy can be installed directly from the Arduino IDE from source code or using a small program (only available on Windows). ESP Easy has a mini web server that allows you to configure the module remotely. Many sensors are supported: Dallas DS18B20, DHT11, DHT22, Si7021 (temperature and humidity) TCR5000 (pulse counter), BMP085, BMP180, BMP280, BME280 (digital barometer) BH1750 (GY-302), TSL2561 (brightness ), Wiegand, PN532 (RFID reader), HC-SR04 (distance), IR, ADS1115 (4 analog inputs 16 bit I2C), PCF8591 (4 analog inputs 8 bit I2C), INA219 (current measurement) … as well as actuators (relay, led, servo, PWM …). ESP Easy also includes a script editor (called Rules) which allows you to create small scenarios.
ESP Easy (R120) or ESP Easy Mega, which one to choose?
There are 2 branches (versions) of the firmware which can cause some confusion when starting out.
ESP Easy is the stable version (R120) that you can get here. Follow this tutorial which explains step by step how to install and configure the ESPEasy R120 firmware on an ESP8266 module. In the event of a problem, use the ESP Tools utility from Espressif. Everything is explained step by step in this tutorial.
ESP Easy Mega is the version under development available here. It embeds a larger number of plugins, a new interface and supports (some) ESP32 development boards. To find out more, you can read this overview article. Attention, to work your ESP8266 card must have at least 1MB of flash memory (be careful to choose your ESP-01 module)