What is "Rubber mulch " like and what are benefits and negatives about putting this under swing set?

Putting Rubber Mulch in my yard was the smartest thing I've done for my kids and for myself. I think it can literally save lives when it comes to kids being kids on the swing-set. My 3 year old daughter fell off the slide, with a weird twist, and landed head first on the ground. I saw it happening and ran over panicking, thinking where I would send my other kid to, while I would took my daughter to the hospital. Miracles of miracles, my daughter just got up and went back up the on slide. I was shaking after because it was a real close call. I chose not to think about what would've happened if I wouldn't have had the rubber mulch there.