# App Overview

An app is a special top-level component whose markup is in a .app resource.

On a production server, the .app resource is the only addressable unit in a browser URL. Access an app using the URL:

https\://*MyDomainName*.lightning.force.com/\<namespace>/\<appName>.app.

**See Also**

- [aura:application](/docs/platform/aura-platform/guide/ref-aura-application.md)
- [Supported HTML Tags](/docs/platform/aura-platform/guide/ref-supported-html-tags.md)