Featured snippet is the neat summary of information that pop up in a separate box placed above the top ten search results in Google page. Technically, a webpage that ranks in Google answer box actually ranks before the #1 position. So, you can also call it #0 ranking.
Google has launched this method to inform the viewer in the better way since 2014. After one year of the experiment, Google made the dominance of Featured Snippet. They also showed that the #0 ranking is actually boosting CTR.
Initially, Google showed featured snippets only for “popular people” or “popular places.”