I learned about the function of a local expert not so long ago, somewhere a year ago. For a while I actively use it in my idioms. Like to share photos of great places. Write reviews about places you’ve been. Most of all, I was surprised by the fact that you can participate in the life of information, now I write not about a comment, but a description of a particular institution. For example, if some place is already closed forever, then you can share it with others by marking it, and not getting into the awkward situation that was with me)