Michael Porter defines a cluster as a geographically proximate group of interconnected companies and institutions that leverage commonalities and complement each other. The document discusses the advantages and disadvantages of clusters, highlighting factor conditions, demand conditions, and firm competition, while emphasizing the role of innovation and infrastructure in sector development, particularly in the context of fuel cell vehicles. The comparison between California and the UK reveals insights into legislative support, cultural factors, and the challenges faced in promoting zero-emission vehicles.