What is featured snippet in Google?

Featured snippets are selected search results that are featured on top of Google’s organic results below the ads in a box. Featured snippets aim at answering the user’s question right away. Being featured means getting additional brand exposure in search results or Featured snippets are special boxes where the format of regular listings is reversed, showing the descriptive snippet first.
We display featured snippets when our systems determine this format will help people more easily discover what they’re seeking, both from the description about the page and when they click on the link to read the page itself. They’re especially helpful for those on mobile or searching by voice.