Arduino is a very popular open-source electronics prototyping platform based on easy-to-use hardware and software. Arduino boards have programmable microcontroller. With some codes, the boards are able to read inputs from sensors, switches and so on and produce outputs like lighting up LEDs, turning motors or activating relays. Using a free IDE (Integrated Development Environment) on your computer, you can write and upload codes directly to the board. The Arduino platform is great for people just starting out with electronics. The IDE uses a simplified version of C++, making it easier to learn to program.
Read the Getting started guide to learn more.
For a quick comparison between different Arduino/Genuino boards, check out this link.
What is Genuino? Genuino, announced in 2015 is Arduino.cc’s sister-brand created by Arduino co-founders, the Arduino.cc team and community. This brand is used for boards and products sold outside the US. The Genuino brand certifies the authenticity of boards and products in line with the philosophy of open-hardware and open-source that has always characterized the values of Arduino. Genuino makes the Arduino open-source project available worldwide through alliances with with local market-leading manufacturers in Asia, Europe, South America, Canada and Africa.
Derivatives Derivatives are boards that are fully or almost fully compatible with Arduino hardware and software. Due to the Open Source Hardware (OSHW) nature of Arduino, any interested party may modify the original design and produce their own Arduino-compatible boards. The creator of these boards usually add value to the original design and manufacture under different brand name.