When you create an app in SharePoint 2013, you choose the type of template it should use. What can be confusing is that apps are often named the same thing as their templates. (For example, an app called Document Library based on the Document Library app template.)
Note: The apps that you have available depend on the SharePoint 2013 edition you use as well as the features that are activated. For example, the Report Library app is available only with the Enterprise license.
The following are some common SharePoint 2013 apps:
Document Library: Holds documents.
Form Library: Holds business forms. This library requires a compatible editor such as InfoPath.
Wiki Page Library: Stores wiki pages.
Picture Library: Stores pictures.
Links: Contains HTML links.
Announcements: Creates and sends announcements.
Contacts: Stores contacts.
Calendar: Creates a calendar.
Discussion Board: Enables users to discuss topics in a threaded forum.
Promoted Links: Creates a place to store links to specific actions using a visual tile-based layout.
Tasks: Stores tasks.
Issue Tracking: Tracks issues.
Custom List: Creates a blank app based on a list.
Custom List in Datasheet View: Provides a datasheet view (similar to the Custom List template).
External List: Connects to external data.
Survey: Conducts surveys.
Asset Library: Stores site assets such as images, audio, and video files.
Data Connection Library: Stores data connections.
Report Library: Stores reports.
Access App: Provides the Office Access web-based app.
Import Spreadsheet: Imports a spreadsheet and its data.