The Buddha's Noble Eightfold Path is divided into three divisions. Wisdom, Morality (Ethical Conduct) and Concentration. Right Mindfulness is the seventh element of the Noble Eightfold Path and is related to Concentration together with Right Concentration and Right Effort.
Mindfulness is at the core of the Buddha Teachings. Buddhist Monks Practice Right Mindfulness by paying attention on their body, their feelings, their mind and mental qualities. They do nothing more than to observe these phenomena with Focus, in a non-judgmental manner. Setting aside greed and distress, desire and other forms created by the Ego.
When Right Mindfulness is present the other seven elements of Buddha's Noble Eightfold Path are present as well. Mindfulness is the state of mind that brings us to the Now. The only moment that is Reality.
We always give our attention to something. Right Mindfulness is to remember to bring our attention back to this moment. Give your attention with all your Heart. Do not compromise. Don't be satisfied with a superficial 'I am fine' when you ask someone you care about how that person is doing.
Through the Practice of Right Mindfulness you will discover new and wonderful things. You will obtain profound insights that you were unaware of. Your increased awareness will enable you to listen with your whole being. Truly understanding what is Reality.
Mindfulness is the quality of fullness of attention, non-distraction. In that sense it is the key to life.