The document defines parts and wholes, and discusses how fads relate to trends. It defines a part as a subdivision that makes up a whole, and a whole as a system of interconnected parts. It states that fads are micro-trends that exist under the umbrella of broader trends, and represent things that gain popularity quickly but may fade, while trends occur on a wider scale over a longer period of time. The document uses the example of mobile phones to illustrate how they started as a fad but evolved into a trend as their use and impact expanded significantly over time.