日本is the native name for Japan. The kanji literally mean sun origin, leading to the poetic description Land of the Rising Sun. It can be pronounced as both にほん and にっぽん, with にっぽん often used for formal or patriotic contexts.
That is how Fuguro works. It brings 日本 back for review right before you forget it, each time a little later, until it sticks for good. You hear it spoken aloud, and you meet it again in stories you can already read. The first five levels are free.