If you've been around long, you've heard about staying hydrated and probably know enough to understand that it has to do with getting enough water in your body. You might even know that you're supposed to drink somewhere around 8 cups of water every day, although the answer to whether that's glasses of water or 8-oz servings could get a little sketchy. But for most people, that's where their water knowledge ends.

So, what does it mean to be hydrated? How do you know you're getting enough water? What are electrolytes? What is the 8 cups of water recommendation really all about?