If you're holding a compass, south is the direction that's directly opposite north. If you're standing in Tennessee, then Mississippi, Alabama, and Georgia will be to the south.
When you need to head south on a hiking trail, you can consult your compass and turn in the direction that's 180 degrees from north. And if you visit the South of France, you'll be staying in the southern part of the country geographically—luckily for you, it's also the warmest, sunniest part of France. The word south has a Germanic root meaning "sun-side."