The Arduino Esplora is a ready-to-use, easy-to-hold controller that lets you explore the infinitive possibilities you have in the world of sensor and actuators, without having to deal with breadboards, soldering or cable.
The Arduino Micro is a microcontroller board based on the ATmega32u4, developed in conjunction with Adafruit. It contains everything needed to support the microcontroller; simply connect it to a computer with a micro USB cable to get started.
The Arduino Due is the newcomer microcontroller board in the Arduino boards family. It’s the first board based on a 32 bit processor (Atmel SAM3X8E ARM Cortex-M3 MCU), which improves all the standard Arduino functionalities and adds many new features.
The Arduino BT is a microcontroller board based on the ATmega328 and the Bluegiga WT11 bluetooth module. It supports wireless serial communication over bluetooth (but is not compatible with Bluetooth headsets or other audio devices).