One of the biggest feature Magento is famous for is its capabilities to develop multi-store and multi-language web stores. Each store can be completely different from its fellow stores. Store Emulation helps developers to emulate any store programmatically.
Suppose you want to send custom transactional e-mail for all stores at the same time as cronjob. When a process run on backend for example cron jobs or email notifications, these processes work under admin store. But suppose if you want to send transactional e-mail on store wise, then email template need grab from store view. You can enable App Emulation and perform this action.
$storeId = 1;
$appEmulation = Mage::getSingleton('core/app_emulation');
// Start environment emulation of the specified store
$initialEnvironmentInfo = $appEmulation->startEnvironmentEmulation($storeId);
* Any code thrown here will be executed as currently running that store
* with applied locale, design and similar
// Stop environment emulation and restore original store