Microsoft Office Web Apps is the online companion to Office Word, Excel, PowerPoint and OneNote applications that enables users regardless of their location to access documents and edit documents. Users can view, share, and work on documents with others online across personal computers, mobile phones, and the Web. Office Web Apps is available to users through Windows Live and to business customers with Microsoft Office 2010 volume licensing and document management solutions based on Microsoft SharePoint 2010 Products.
Office Web Apps is tightly integrated with SharePoint 2010 Products. When you install Office Web Apps, the Office Web Apps Services are added to the list of SharePoint Services and the Office Web Apps Feature is added to the available SharePoint Features.
Office Web Apps services include the Word Viewing Service, PowerPoint Service, and Excel Calculation Services that are created and run within the context of SharePoint Services.
The Office Web Apps Feature and services integrate with SharePoint’s robust enterprise content management capabilities to provide users the ability to access and work on your organization’s documents from anywhere using a Web browser.
For More Detailed Information check the Below link .