[mkarr]

When the ESP8266s were first introduced, they came with a closed firmware that simply responded to AT commands over a serial port. To do anything with the chip, you had to have another micro controlling it.

However, sometime after the hobbyist/maker market started to take notice of the devices, an SDK was released, allowing for code to be run natively on the devices without a separate micro.

Nowadays, there are multiple options for running code on the devices. You can do it natively via C/C++ with the SDK, or you can try out one of the other firmwares that various parties have produced, like NodeMCU (Lua) or MicroPython.

The chips are actually pretty damn powerful compared to the Atmega series micros used with the classic Arduinos. And cheap too. You can get a NodeMCU module that already has a voltage reg. and USB->UART controller on it for around $3. Very hard to beat.