What is the difference between Arduino board and Genuino Board?
The name Genuino grew out of the split between Massimo and Gianluca (aided in part by Microsoft of course, and a trademark wrangle that went wrong). Each side wanted to appear to be more "genuine" than the other. That lead to the "Genuino" name (a genuine Arduino), and a version number war with the IDE.

Both sides started making their own variants of boards, with some only available from the USA (Arduino) and others only outside the USA (Genuino).

Since they have patched up their differences now the two boards are one and the same. A Genuino Uno and an Arduino Uno are the exact same board. They always have been, there has just been arguments over the name.