The ESP-01S, ESP8266 WiFi Module is a self-contained SOC with integrated TCP/IP protocol stack that can give any microcontroller access to your WiFi network. The ESP8266 is capable of either hosting an application or off loading all Wi-Fi networking functions from another application processor. It is very useful for simple IoT.
This module has a powerful enough on-board processing and storage capability that allows it to be integrated with the sensors and other application-specific devices through its GPIOs with minimal development up-front and minimal loading during runtime.
ESP8266 WiFi Features:
1. 1MB (8Mbit) Flash size.
2. Very competitive price
3. AP, STA, AP+STA modes available.
4. Very simple AT commands, easy to use.
5. Internal LWIP interface.
6. Four pins interface, VCC-3V3, GND, TXD, and RXD. Two extra GPIOs can use.
7. AT commands firmware. New IC ESP8266ex.