You can set up a single store within a community as well as multiple stores within the same community. Communities are used to segment users. For example, if you want users to view all your storefronts, you can create one community with multiple storefronts. In case, you want to restrict the set of users to different stores, you must create separate communities to restrict access.
You can achieve this by creating different visualforce pages and control access through profiles and permissions sets.