The book I read to research this post was Arduino: A Complete Guide by Tech Guru which is a very good book that I read at kindle unlimited. There are 3 variants of the Arduino in the book. The Arduino Uno is the one most people use and is fairly basic but cheap. It has sensors that can measure things and are 5 volts.It is powered by the USB port. It will also connect to a computer monitor. The Arduino Mega 2356 is the high end version on a larger board. There are many programs on the internet but not as many as the Uno. It has a variety of sensors and can be powered by USB. Then there is the Arduino Pro designed to go in electronic kit projects and with out USB. The Arduino in general will run its very own version of linux found at http://arduino.cc. It has its own programming language like a cross between C/C+ and Java. The Arduino is more strongly built than the Raspberry Pi. Many people use solderless breadboards for doing experiments with it. Because they are solderless the circuits can be set up and taken out easily and the components can be used for different projects. You also need a multimeter which at the very least should measure current, resistance and potential difference or voltage. This book is only around 40 pages so is quite short and I enjoyed reading it and do recommend it.
