This chapter covered an important subject in Computer Vision. Motion detection is an essential task, and in this chapter, we have provided the reader with the insight and samples that are required for the most useful methods available in OpenCV: working with video sequences (see the videoCamera example), the Optical Flow technique (see the maxMovementLK and maxMovementFarneback examples), tracking (see the trackingMeanShift and trackingCamShift examples), the Motion templates (see the motionHistory and motionGradient examples), the Background subtraction technique (see the backgroundSubKNN example), and image alignment (see the findCameraMovement example).