What is an App in SharePoint 2013

App is similar to a web part. One main key difference is everything is at the client side and not on the server side when you write a code developing an app which is called client web part.

In SharePoint 2013 Lists and Libraries are now termed as apps.

SharePoint now has its own app store where we get some free apps and some paid apps which can be installed and then can be used inside SharePoint.

There are three hosting options when you create app for SharePoint.

1) SharePoint hosted - On Premises.

2) Externally hosted

3) SharePoint Online - Sandbox solutions can be created. (deprecated now in SharePoint 2013) or new apps web part (client web part) can be used.

Certain important points about an app are :

• App cannot have any server side code.

• Apps get created in a special “app web” on a special URL which is isolated from the original SharePoint web. Each app is a part of dedicated site collection.

• App does not have permission to talk to the parent site or site collection

• App cannot talk to the host site. ( a site in which app is displayed)

• Apps can be created using Visual Studio 2012 or using "Napa" Office 365 Development Tools

So SharePoint 2013 apps do not live in SharePoint rather they execute within the browser client or in a non-SharePoint server such as IIS or Windows Azure.

 

Apps can only be added by users with Full Control permission to the site. As mentioned earlier Apps can be installed from the centralized app store from on premises SharePoint or from public app store.

Apps can also be opened as a full browser screen or can also be a part of page. When we want app as a part of page we can use app part just like a web part to display that app in the app part. App part will display content of that app part in Iframe html element.

Regardless of how you authenticate your app with SharePoint, you need to have user consent to perform actions. You declare the required permissions in the app manifest file while developing, and the user is asked to grant or deny those permissions to the app during installation.

You can connect your app with just about any internal or public web services, take advantage of the new OAuth 2.0 support in SharePoint, and use the Representational State Transfer (REST) and client APIs (JavaScript and .NET) to integrate and connect your app with SharePoint.

There is a list of available apps that can be downloaded (some free / some paid versions) from Microsoft market place for SharePoint 2013.

Microsoft App Market place for SharePoint 2013

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