You probably need to listen to a variety of music from each genre and take note of the instruments used, the style of singing, the rhythm and tempo, as well as the themes they sing about. This will help you to understand and describe the differences better. Have fun!

They are very different. (But both styles are enjoyable) If you want to understand the sound of reggae, listen to the Bob Marley album called "Legend". It has his most famous songs. If you want to understand country music, listen to the Willie Nelson song called "Crazy"(1961) or his song "City of New Orleans." Good luck!