The difference between the two lies in definition and purpose, location and environment.

1. Definition and purpose: Outdoor advertising is a widely spread publicity medium designed to convey information, promote products or services, and attract potential customers through various forms of advertising. Outdoor signs, on the other hand, focus more on enhancing brand image and visibility, often including elements such as logos, names or trademarks.

2. Location and environment: Outdoor advertising can be displayed in various locations, such as streets, bus stops, shopping malls, etc. They usually choose the right location based on their target audience and marketing strategy. Outdoor signs are usually placed near a business or location to identify and guide customers.