Companies spend billions on advertising globally to establish brands and sell internationally. Advertising involves various players like advertisers, agencies, suppliers, and media. Approximately half of all US advertising is local, targeting customers within the same city or county. Regional and national advertisers operate in multiple states or regions. Advertising types include product, sales, institutional, and classified ads. Agencies work solely for clients, employing creative and business professionals. They provide services like planning, research, media buying, creative work, and production coordination. The relationship between agencies and their clients is important, developed through networking, presentations, chemistry, and reviews.