Question: 1. what are the differences between the arduino uno and arduino leonardo?
Answer: Uno has 20 digital I/O pins, 6 of which are also analog input pins. Leo has 23 digital I/O pins, 12 of which are also analog input pins. Uno has 3 digital pins on the ICSP header which are repeats of pins on the digital header, pins 11, 12, and 13.