Frozen shoulder, also known as adhesive capsulitis, is a condition characterized by stiffness and pain in the shoulder joint. It typically develops slowly over three stages - freezing, frozen, and thawing. The freezing stage involves increasing pain with movement over 6-9 months, while the frozen stage sees worsening stiffness for 4-12 months. Treatment focuses on physical therapy, manual therapy techniques like stretching and mobilization, medications, and sometimes surgery.