POI is the acronym for Point Of Interest. That’s Google’s term for standard still photo images of a business and is used to distinguish those images from the panoramas of a virtual tour. POIs are uploaded to Google’s servers along with your Street View tour and appear in the image carousel at the bottom of the screen that shows the details of your business on Google Search and Maps.
Google has a list of POIs that they want to see, such as the building facade, signage, and wide-angle shots of the interior. Any additional POIs are up to you, and can include things like close-ups of products or displays, and rooms that aren’t part of the main tour.