Google is apparently testing out a new feature for business listings that allows users to ask questions about a given establishment, then get answers from other users, or even the business owners themselves, if they happen to see the question. The feature is currently hitting some users on an extremely limited basis, and there seems to be no particular criteria for a user to be considered eligible for the testing. It should be noted that all of the screenshots of the test captured so far depict either the official Google app or the Google Maps app, both on Android and iOS, so you may need to have it up to date in order to participate. It is also worth noting that the source of most of the screenshots is able to access the feature in the Google app and Maps, but the blogger in the source link is only able to access it in Search. In any case, Google has yet to make any official statement on the new feature.
For those who are on board, the way it works is actually pretty simple. As seen in the screenshots below, all you have to do to leave a question is pull up a listing for a given place or business on the Google app, then enter some text into a text box below any pictures the listing may have, just under the label "Questions & Answers". If there is already a question present, you'll be able to see it in the listing. Just give it a tap, and you can leave an answer. There may be extra features for business or place owners, such as being able to request having questions removed or getting a notification when they're asked, but there has been no word on anything of that sort thus far.
This feature has not yet been announced, so it is quite likely that the rollout will stay very small for the time being. If you would like to get in on the testing, there are no surefire ways, but being active with business and place listings, such as by becoming a Local Guide in Maps, will at least keep you viewing listings often. If the test does happen to roll out to you, you'll see it sooner if you're accessing listings more often. Obviously, there is no official timeline for a wider rollout at this time, though it's likely not too far off, if everyday users are getting a chance to test the feature.