Term Store-Site Column-Content Type in SharePoint 2013
1.Create new term store
2.Create a Site column with data type as meta data.Select term store while creating Site column
3.Create Content type.
4.Add existing site columns, select Site column which you have created in the Step 2
5.Create a Document library, Add Content type which you have created.
SharePoint 2013 Apps
Host Web: Site Where users add an app.App is available via site contents, app parts, menu items, or ribbon.
Isolated App Domain: for isolation, apps run in a URL space separate from host web