Explain GD&T concepts such as symbols, feature control frames, datums, tolerance zones, types of tolerances, geometric controls, and practical applications in manufacturing drawings. Discuss limits, fits, and interchangeability. Cover gear basics including types of gears (spur, helical, bevel), gear terminology like module, pitch, pressure angle, backlash, gear ratio calculations, advantages, applications, and common problems encountered in gear systems during operation and design.