Featured snippets are the search results that give the best answer to your query from all the SERPs. Usually a featured snippet is at the top of the first page of Google, but if there are Google ads competing for the same keyword or search query, the featured snippet is displayed directly below these ads, above the organic search results.
With a featured snippet, the reach is much greater, people click on the meta title more often and there is more traffic on your website. Unfortunately, you cannot control when you get a featured snippet. However, you can increase the chance of a featured snippet by designing your website in a SEO-proof way. You can do this by using authoritative links, an H1 and H2 title, but the most important thing is to write valuable content.
Featured snippets can also be used in email marketing. Featured snippets highlight the first few sentences of, for example, a newsletter, so that the reader becomes curious and more likely to open the email.
Besides featured snippets, there are also rich snippets and turbo snippets.