What is the 30 day shred I keep seeing people talk about?

It's a serious, no joke 20 minute workout. I started Monday and was super busy last night so didn't get a chance to do it, but just from the workout on Monday, I am sore all over still. I am looking forward to doing it again today. I like that Jillian isn't even in the room with you, yet I still feel like she is right there yelling over my shoulder telling me to push harder! I love it! It's important to note that while she recommends doing 10 days of each of the three levels, you should def go at your own pace. Once level one starts getting pretty easy, I would move on to the next level. That's what I plan on doing and then I am going to try Ripped in 30 after I complete the 30 Day Shred. GL!