Cloud App Model has made it possible to build new dimensional apps that combine web technologies and cloud services. It can be hosted on cloud; it enables faster deployment, up gradation facility and easy maintainability option. Now developer have the ability to publish and sell apps through a new Office Store, or distribute IT approved apps through an internal App Catalog. Doing this Microsoft offer a “Cloud App Model” that incorporates Web standards that  indicate developers will code in HTML, client-side ASPX, CSS and JavaScript.

What is Napa?
“Napa” is a toolset come with new SharePoint and office release that has made a path to start building apps for the new Cloud App Model. We wanted to provide a lightweight, in-browser experience, so that you could quickly build SharePoint or Office web app in the same browser where they would run. Napa is web based nothing need to install to start development. For more feature it possiable to start Visual Studio 2012 IDE.
Napa Coding Features includes:
<div class="MsoListParagraphCxSpMiddle" style="margin:0 0 0 1.5in;text-indent:-.25in;">a.  Indenting</div><div class="MsoListParagraphCxSpMiddle" style="margin:0 0 0 1.5in;text-indent:-.25in;">b.  bracket matching </div><div class="MsoListParagraphCxSpMiddle" style="margin:0 0 0 1.5in;text-indent:-.25in;">c.  text-based auto complete</div><div class="MsoListParagraphCxSpMiddle" style="margin:0 0 0 1.5in;text-indent:-.25in;">d.  instance highlighting</div><div class="MsoListParagraphCxSpMiddle" style="margin:0 0 0 1.5in;text-indent:-.25in;">e.  syntax colorization</div><div class="MsoListParagraphCxSpMiddle" style="margin:0 0 0 1.5in;text-indent:-.25in;">f.   edit app manifest</div><div class="MsoListParagraphCxSpLast" style="margin:0 0 10pt 1.5in;text-indent:-.25in;">g.   properties via a lightweight visual designer</div>It is possible to build mail apps for Office, content apps for Excel and functionality to Excel documents, and task pane apps for Office and Word documents in a task pane adjacent to the document. It’s new opportunity for software development companies to market their apps via Microsoft’s  new Office Store, or distribute them within organizations via an internal app catalog.