Nike is the largest seller of athletic apparel and footwear worldwide, with $18.6 billion in total revenue in 2008, mainly driven by footwear sales. The company aims for a 50% revenue increase over the next five years, focusing on service and product differentiation, strong brand image, and marketing strategies. Key competitors include Adidas-Reebok and Under Armour, and Nike maintains a significant market presence in the U.S. and globally through innovation and customer customization options.