Meditation is to try to get past the "thinking" mind, and into a deeper state of relaxation or awareness.
Meditation is a common practice in many religions including
Buddhism, Christianity (sometimes), Hinduism (where Yoga is important) and other religions.
Buddhism, three things are very important: being a good person, making the mind stronger, and understanding why people are in pain ( Dukkha). 
Buddhist meditation is not just used for
spiritual reasons. Research shows that Buddhist meditation lowers stress, anxiety and depression. 
Buddhists, meditation is used to calm the mind so that the mind can better see the cause of pain. Buddhists believe that this type of seeing can end pain. 
Most types of Buddhist meditation focus on something. The most popular things to focus on include the
breath, love, other emotions, and religious images and sounds. 
Christians sometimes meditate by thinking about small parts of the
Bible, or by saying the words of a prayer to themselves over and over.
↑ In Buddhism, these three things together are called the "threefold training." In the words of 2,000-year-old Buddhist books, these three things are called sīla, citta (or samādhi) and paññā. See, for example, Thanissaro (1998a) and Thanissaro (1998b).
↑ Kabat-Zinn (1990); and, Linehan (1993), p. 1.
↑ See, for instance, Thanissaro (1998c).
↑ See, for example, Kamalashila (2003).
Kabat-Zinn, Jon (1990).
Full Catastrophe Living: Using the Wisdom of Your Body and Mind to Face Stress, Pain, and Illness. NY: Dell Publishing. ISBN 0-385-30312-2.
Linehan, Marsha M. (1993).
Skills Training Manual for Treating Borderline Personality Disorder. NY: Guilford Press. ISBN 0-89862-034-1.