The ESP8266 development board has several components integrated. These are:
1 DHT11 temperature and humidity sensor
1 potentiometer to generate different voltage at the ADC pin
1 RGB LED
On the board there is also a usb/serial converter to directly connect the board to the PC and a voltage regulator, which generates the 3.3V for the ESP chip. The board comes with the ESP module.
It is breadboard friendly and has an antenna connector. The second board does have all the other components. The different components on the board can be enabled separately using some DIP switches. All external pins of the ESP module are also accessible via pins on the board. So, you cannot only work with the on-board components.
The USB/serial converter on this board is a CH-341 chip. It did work out of the box on Debian Linux, but not on OSX and Windows. Drivers for thus operating systems can be downloaded here: