Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists and anyone interested in creating interactive objects or environments.
It actually is a single-board microcontroller designed around an Atmega328 with an USB interface, 6 analog inputs, as well as 14 digital I/O pins which allow to attach various extension boards or applications. The integrated development environment (IDE) is open source and allows to write programs for Arduino using Processing language.
Of course, right from the first experiments, blending Arduino with two stroke motorcycles was inevitable. Lots of people have constructed a lot of useful staff, from shift lights and data loggers up to complete CDI units...!