People have been continuously mesmerized by the sci-fi notion of controlling things based on hand gestures. However, only a few ponder upon the working of these gesture-based systems. This chapter explains how these gesture-based systems generally use skin-colour-based hand segmentation techniques. This chapter sheds light on and explains various colour models, various methods to use these colour models and perform skin-colour-based hand segmentation, various real-life applications of segmenting areas using skin-colour with multiple examples of hand gesture recognition, as well as other applications where skin-colour based segmentation is used.