This is a plastic access door that you mount using adhesive (not included) to drywall. It is an aesthetically nice way to cover up a hole you might have from a water meter, gas meter, sewer cleanout, etc. Once you glue it to the drywall, it is easy to open the access door with a flathead screwdriver or similar. Then you can just snap it back shut. I bought it several years ago but never used it. So it's basically brand new. Here is more information on the product:
https://www.acudoraccesspanels.com/18-x-18-flush-plastic-access-door-acudor/