Let me just start by telling you that BOSU is an acronym of sorts for both sides up. That's kind of cute, but I can’t help but think about Ginsu knives (only $99.99 for the entire set) when I say it.
You’ve probably seen one at your gym. It looks like a physio ball cut in half. You can work with either the flat side up or the ball side up - hence its name. Even though there are only two options, you'd be surprised with the amount or exercises you can do with the BOSU. The variations are endless.
With the ball side up you can stand on it, test your balance and work your core. Or just stand on one leg to strengthen your standing ankle. Another possibility is lunging with your front foot on the BOSU.
With the flat side up, you can do a plank. This is really hard and I would start on your knees (make sure you’re on something cushy to protect your knees).
Many gyms offer BOSU classes. Click here to find a class near you.