What are stand-alone apps in Aura in Salesforce Lightning Components?

Hi Deepal,

The standalone lightning app has a custom URL. These can be hosted and run using the URL directly. Standalone apps file has .app extension. You can use aura components inside standalone lightning apps.
Using standalone lightning app is mandatory in some scenarios like-
1. Using lightning out to host aura component outside Salesforce ecosystem.
2. Using aura component within a visualforce page.