Magento 2.0.18 is the final 2.0.x release. After March 2018, Magento 2.0.x will no longer receive security patches, quality fixes, or documentation updates. To maintain your site's performance, security, and PCIPayment Card Industry: Refers to debit and credit cards and their associated businesses. compliance, upgrade to the latest version of Magento.
When Magento Commerce 2.0 is installed, a main website, and store view are created. You can create additional websites, stores, and store views, as needed. For example, in addition to your main website, you might have a additional websites with separate domains. Within each website, you can have multiple stores, and within each store, separate store views.