A back stretch involves moving your spine through flexion (rounding) and extension (arching) or twisting, often starting on hands and knees (Cat-Cow) or lying down (Knee-to-Chest, Supine Twist), to relieve tightness, improve mobility, and ease pain by elongating muscles like the latissimus dorsi, trapezius, and rhomboids in the upper, middle, and lower back. Key stretches include the Cat-Cow for spinal mobility, Knee-to-Chest for lower back/hips, and Supine Twists for spinal rotation, focusing on gentle, controlled movements and deep breathing.