What is mindfulness?
The most straightforward definition of mindfulness is one used by Jon Kabat-Zinn, the originator of Mindfulness-Based Stress Reduction. Mindfulness is "simply a way to pay attention on purpose, in the present moment, and nonjudgmentally."
In other words, it is nonjudgmental awareness of now. Mindfulness meditation can cultivate this way of paying attention, which eventually becomes a way of being. It allows us to see things as they really are, to be both participant and observer at the same time. This bare attention to life can lead ultimately to acceptance and contentment.