The Arduino UNO remains one of the most popular microcontrollers on the market today. Its huge success is due to the fact it makes it so easy to create programs and prototype electronic systems, so anyone can get involved in the Internet of Things revolution. The delevelopment environment, where you create the programs to control the hardware, is based on C++ and since the Arduino platform has been established for a few years now, there is no end of tutorials and code snippets available on the internet to help you get started.
Although the Arduino UNO is the most popular board, there is now a whole range of derivative boards based around the same Arduino environment and programmable in the same software. If you need more inputs than the UNO provides - use an Arduino Mega, if you need fewer but are more interested in getting the smallest board possible - consider the Adafruit Trinket .