If you are running Magento 2 with a sub-folder for each store view or website then your index.php file will often have code like
$params = $_SERVER;
$params[\Magento\Store\Model\StoreManager::PARAM_RUN_CODE] = 'my_store_view_code';
$params[\Magento\Store\Model\StoreManager::PARAM_RUN_TYPE] = 'store'; // store or website
$bootstrap = \Magento\Framework\App\Bootstrap::create(BP, $params);
This tells Magento which store view to load. This is just a reminder to update this code if required.
Sometimes this is also done via a .htaccess file or similar depending on how you have chosen to configure your server.