Which type of advertising involves commercials placed by major advertisers to reach a nationwide audience?

Network advertising is characterized by commercials placed by major advertisers on national television networks to reach a large, diverse audience simultaneously across multiple markets. This approach allows advertisers to benefit from the broad reach of networks, which broadcast their programs across various regions, ensuring that their message reaches consumers on a large scale. The coordination with networks makes it easier for brands to promote their products or services effectively, as they can target viewers who tune into popular shows watched nationwide, such as prime-time dramas or major sporting events.

In contrast to network advertising, local/adjacencies refers to commercials that target specific local markets and are shown during the breaks of national programming, which limits the reach. National spot advertising involves targeted ads placed in specific markets, but it's not as comprehensive as network advertising since those spots are limited to certain geographic areas rather than a full national reach. Barter syndication involves the trading of ads for programs without cash exchange, typically relying on local stations to broadcast these programs, hence it does not have the same extensive audience that network advertising provides.