Mindful Monday: What the Actual Heck is Mindfulness?

I recently realized that as much as I talk about the importance of being mindful, I haven't been so mindful of explaining what the heck mindfulness actually is. And how to do it. Thus, I committed the cardinal sin of mindfulness. Assuming. I figured because "mindfulness" is so hot these days that everyone already knows what it is. But come to find out, not so much.