Deep tissue gets deeper into the muscle tissue, muscle fibers and fascia.  It is aimed at getting to the underlying issue.  It often requires a deeper firmer pressure that can result in feeling sore or bruised the next few days. It is important to communicate with your therapist on the pressure at all times.  You should never be holding your breath or being in pain.  Deep tissue uses techniques of sports massage, medical massage, and myofascial release.

Make muscle movement easier
Increase range of motion
Lower blood pressure
Ease muscle pain