In SharePoint 2013 App development an App part is a Container Frame for your App. We all know that App runs in an Isolated web app and this may not seem useful when you want to rather display an App as a WebPart. Well an App Part is just for that requirement.
What is an App Part? A Way by which an App for SharePoint can be surfaced is through an app part. It is a type of Web Part that is represented by the ClientWebPart class.
How is App Part Different than a WebPart?
An App Part is essentially a wrapper for an IFrame that would host a page of the app. In addition to acting as a Wrapper, like a WebPart an App Part can have Custom properties that users can set in a Tool Part. Such properties could be used, for example, to set context information such as the user’s ZIP Code or Postal Code etc.
Summary : SharePoint 2013 – What’s “App part”?, Features and Benefits of using App Parts in SharePoint 2013
How do I Create an App Part for my App?
ClientWebPart.aspx in a SharePoint Hosted App will act as your App Part Interface. The backend code will still be in App.js. To include an app part in your app, you create a host web Feature in the app and add declarative Web Part markup. Like any other Web Part, it appears in the SharePoint 2013 Preview UI from which users add Web Parts. You can have more than one app part deployed with your app if you need even more variability.
Features and Benefits –
* Its a kind of WebPart for your App or a webpart to Display Content of the hosting App on one of the Existing SharePoint pages.
*Like WebPart you can add Custom properties to the App Part as well.
* You can have more than one app part deployed with your app.
* The two parts can have different sizes and functionality.
*You can also deploy app parts to the app web.