I'm so glad Jess asked what a reverse lunge is...remember, I LOVE the questions, and I want to answer them so don't be shy! Reverse lunges are great if you have weaker knees because they are a little less impactful on the knees than forward lunges, and they work the same muscles. They are also great for keeping your form in check, which is very important.
1. Start in a standing position.
2. Step your right leg as far back as you can and lower yourself down into a lunge.
3. As you come back up step your right leg back to your start position.
4. Repeat the same movement with you left leg.
You'll want to step back as far as you can, and go as low as you can to get the maximum effect. Be sure to watch your front knee/toes. You don't want your toes going over your knees. Keep them right in line. Hope that helps!