Schema.org is a collaborative project launched by major search engines like Google, Bing, Yahoo, and Yandex to create a standardized vocabulary for structured data on the web. This vocabulary helps webmasters and developers mark up their content in a way that search engines can easily understand, improving the visibility and relevance of their web pages in search results. By using Schema.org markup, websites can provide additional context about their content, such as articles, events, products, and reviews. This structured data can enhance search engine results with rich snippets, making it easier for users to find the information they need quickly and efficiently.