Mindfulness is just totally paying attention to whatever it is you are doing, being mind-ful of it instead of yourself or anything else.

Broadly, it's about action rather than feeling. How we feel can't do anything, only what we do "matters" and what we do is based on what we think, our mind, and what it's doing.

It's about focus and seeing what is in front of us in all of its myriad beauty and detail.

I like this mental health use of it: http://www.todoinstitute.org/