This is the major and important step for any online storekeeper to determine which product falls under which category. The categories that you create here will not only streamline your products but also will be visible on your store's product listing page.
Your customers will be able to use these categories as filters to sort out the products they wish to buy. And for this, you have to know how to add a new category for New Products & Existing Products.
By going to Catalog --> Categories, you can perform multiple actions on your existing categories like - view all the products in a category, check the total count of active/published products of a category, you can edit a category or delete a category, and add new categories to your products.