Questions on SharePoint Apps

I am still trying to wrap my head around SharePoint Apps and have a few questions around this.

1. When I deploy an App using Visual Studio where does it get actually deployed to.  What is the process of deploying an app if I am not using Visual Studio.?
   
2. If I purchase or get a free app from the App Store
   a. Where does this information go, is it stored in Central Administrator?
   b. How do I remove the app?
   c. Apps obtained from the App Store gets available to the whole organization, how do I restrict this?
   
3. When I deploy an app created through Visual Studio its only available to the Web Application which I deployed the App to, how do I make this App available to other SharePoint Web Applications as well?