What is Google's Rich Answer Box?

A "rich answer" is any attempt by Google to answer the searcher's query in search results in a way not requiring a click through to a website.
Rich answers come in many forms. They can be recipes, sports scores, stock graphs, calculators, sliders, text-based answers, numbered step-by-step directions, maps, and much more.

you may have noticed that when searching for a term or asking a question on Google, you receive not only a list of search results but also an informational box at the top of the page that displays a quick answer to your question or a description of your search term.

When we put some query in google search box, the first result in SERP that appears with a box around it is rich answer box. The benefit of rich answer box to the user is the answer is displayed on the SERP itself, the user does not have to go to a specific result and find the answer.

A "rich answer" is any attempt by Google to answer the searcher's query in search results in a way not requiring a click through to a website

Google's rich answer box is a relatively new feature that provides searchers with direct answers to their questions at the top of the search page. When a searcher types a question into the Google search bar, Google scans through its search results to find the closest answer to the question. When the search engine finds an answer to the question, it will feature a snippet of the website's page at the very top of the search results page. In
addition to the featured snippet, the rich answer box will provide a direct link to the page from which the answer came.