Why we need Programming in SharePoint?

Although SharePoint 2013 consists of several reusable, Out-of-the-box solutions, still custom solution requirements are kept unaddressed.
SharePoint provides API to address this problem.
Through the help of developers custom solutions can be built and integrated with SharePoint.

What are the kinds of Solutions available?

Custom Solutions can vary from:

1. Custom Web Part
   
2. Client Application integrated with SharePoint
   
3. Timer Job working in SharePoint Server
   
4. SharePoint Apps
   
5. Mobile Application
   

What are the kinds of APIs available?

SharePoint provides different set of APIs. We have to choose the optimized one based on the type of solution & skill availability:

1. Apps for client side
   
2. Farm solutions for server side
   
3. Mobile API
   
4. Silverlight API
   

In the Client App model we can use HTML, JavaScript combinations as well.

Please note that Sandboxed Solutions from SharePoint 2010 are deprecated. Farm Solutions can be created though.

Development Tool

Visual Studio 2012 is the best tool available for SharePoint custom solution development. You can download a copy from the following location:
http://www.microsoft.com/visualstudio/eng#downloads

Which API to use?

Depending on the scenario you can use the appropriate API set.
If you need custom web part solutions available for the users, purchasable over store, you can use Apps.

If you need an Administrative Application to manage SharePoint objects, create a Timer Job, use Server Object Model.

If you have a machine outside server network & still need to bulk manage the SharePoint objects, use Client Object Model.

References

Choosing Right API http://bit.ly/ZVpDjt

Summary

In this article we have explored about the Programming API available in SharePoint 2013. In the next articles we can explore each programming models with sample application.