@sweta, you seem to have answered your own question. The "Explore Categories" is being pulled from the info that you are providing in your GBP, specifically the Products you manually created. If you don't want that section to show or to be named differently, you'll need to either delete the Product with that same name, or rename the Product to the name/description you want shown. If you are wanting different Products to show up in the "Explore Categories", I don't know of a way to influence Google to do that other than possibly to remove the unwanted Products Names so you are only left with the four you would like to show up under Explore Categories.