You can extend Office 2013, Office 2010, and Office 2007 by using Office developer tools in Visual Studio. These tools include project templates to help you create Office solutions by using Visual Basic or Visual C#, and visual designers that help you create custom user interfaces for your Office solutions.
If you want to create solutions that deeply integrate with Office and leverage the power of the .NET Framework, an add-in or customization might be a great option. However, if you're looking for a new way for users to interact with Office customizations, apps for Office is a great place to start.
Office 2013 and Office 2010 solutions using Visual Studio 2013 or Visual Studio 2012
Office 2010 and Office 2007 solutions using Visual Studio 2010
Meet apps for Office
Deploy, update, and maintain your apps faster in the cloud. Publish and distribute IT approved apps within your organization using an internal app catalog, or sell your apps in the Office Store.
Connect to the largest install base of users for any productivity services so your app will be exposed to the largest potential audience possible.