Mindfulness is the practice of purposely bringing one's attention in the present moment without judgment, a skill one develops through meditation or other training.
Though definitions and techniques of mindfulness are wide-ranging, Buddhist traditions explain what constitutes mindfulness such as how past, present and future moments arise and cease as momentary sense impressions and mental phenomena.
Clinical psychology and psychiatry since the 1970s have developed a
number of therapeutic applications based on mindfulness for helping
people experiencing a variety of psychological conditions. Mindfulness
practice has been employed to reduce depression, stress, anxiety, and in
the treatment of drug addiction.
Clinical studies have documented both physical- and mental-health
benefits of mindfulness in different patient categories as well as in
healthy adults and children.
Read more about mindfulness here.