The following was taken from Lynda Klau’s blog

“Mindfulness is the practice of bringing our awareness to what we are experiencing in the present, both internally and externally, without judgment (Kornfield, 2009). It is a wake-up call to become conscious of the ways we perceive and respond to life’s situations. When we live mindfully, we shift our entire ground of being.”

Rather than me try and explain it here is a TED talk with a basic introduction.