Introducing Sharepoint 2013 Apps

SharePoint 2013 provides a new concept of developing or extending the websites. It is refereed as 'Apps'. SharePoint Apps consist of self contained functionality to extend the capabilities of websites in the share point. Users can simply go to Office store by redirecting to (http://office.microsoft.com/en-us/store-FX102759646.aspx) to purchase an app and install them on their websites. To build an app, refer dev.office.com.

Building an App via Cloud App Model

The cloud app model is a loosely coupled model which provides developers an opportunity to create 'Apps for SharePoint' by selecting the technologies and programming language of their choice.

Developers can use Html and Javascript for developing the presentation layer and Php, Asp.Net along with db such as MySql or Sql Azure etc; for defining business layer. So the business logic would be running either on Windows Azure or on your hosted server outside the Sharepoint premises but still running and accessible within the SharePoint website.

Before deciding what language a developer is going to use and how to host an app in Sharepoint, lets discuss the hosting options that Sharepoint offers;

1. Sharepoint hosted apps: These apps donot have any server side code and use Javascript client object model to access the objects of Sharepoint. The code is a combination of HTML and Javascript.

2. Cloud hosted apps: These apps allow developers to write server side code. These apps are further divided into two categories;

• Auto Hosted App: The Auto hosted app are only supported for Sharepoint online(Office 365). The business logic(server side code) is hosted on Windows Azure. When a customer installs 'Windows Azure Auto App' from market place, a new website is created on Azure. The app can also contain a Sql database that will run on Azure on deployment. The website is then loaded in the SpFrame(Iframe) in the Sharepoint. The basic advantage in the Azure hosted app is that developers doesnot have to take care of the components that are going to deploy seperately. Sharepoint itself deploy the components in the Azure[1].
• Provider Hosted App: For provider-hosted apps, you or your IT department hosts the app on a dedicated server or third-party hosting service. These apps run on your server or in the cloud, depending on how you choose to host your app.

References: 

1. http://msdn.microsoft.com/en-us/library/fp179887.aspx