where share point hosted apps will be stored? and is there any difference between APPWEB and HOSTWEB?
The SharePoint hosted apps are stored in the same site collection as the host web and facilitated by the App Management Service Application. The host web is the SharePoint site in which the app in question will be displayed or installed on. The app web is a small web instance that is created whenever the installation of an app occurs. Each app has it's own app web and is logically unrelated to the host web.
The host web will have a normal URL like http://sharepoint.domain.com
The app web will have a generated url like: http://app-2b9ff0d7b408ce.appdomain.com