Ok. What exactly is 'deep learning'?

Hello all,

I have done some ML, and being somewhat plugged into the scene, I keep hearing about deep learning this and deep learning that.

For all the blogs/articles/soundbites I come across however, I cannot seem to come across just what exactly deep learning is. Its starting to sound like a buzz word unfortunately, but maybe there is some gold in the ruff.

So, what is deep learning precisely? What will it help us do differently, and how? If you feel you can couch it in terms of supervised/unsupervised learning, all the better, with the constraint that the explanation still be precise, clear, and intuitive.

Thanks! :-)