In marriage counseling, a therapist is a licensed mental health professional with specialized training in psychology, counseling, or social work. They are equipped to diagnose and treat emotional and psychological issues that may be affecting the relationship. A coach, on the other hand, is typically not a licensed mental health professional but may have expertise in relationship coaching and provide guidance and support to improve specific aspects of the relationship, such as communication or conflict resolution. It's essential to choose the professional that aligns best with the couple's needs and goals.