What is SharePoint 2013 (Preview) -
A new version of Microsoft famous Collaboration portal called SharePoint. The version adds few new exciting features such as Social Feed,SharePoint Apps and cross-site publishing.
Development Changes –
Tools – SharePoint 2013 has Introduced new Tools for App development. Visual Studio 2012 now lets you develop apps for SharePoint and apps for Office. In addition a new web-based tools called “Napa” Office 365 Development Tools were introduced for developing apps.
No more Sandbox solutions. SharePoint 2013 sandboxed solutions are deprecated. So all we got is the New App model and the Old SharePoint Farm solutions. check out SharePoint 2013 – Apps Vs Farm solutions