'Mindfulness is a specific way of intentionally focusing on your thoughts, feelings and the world around you, moment by moment.

It encourages clients to be aware of each thought, so they can ‘catch’ and manage a negative thought before they become overwhelmed by a stream of negative thoughts and feelings. This can help to reduce stress and anxiety and help clients to positively change the way they see themselves and their lives. 

Mindfulness-based therapists can work with individuals and groups and will usually integrate mindfulness with another therapeutic approach'. 

Ref: http://www.bacp.co.uk/student/modalities.php