SharePoint 2010 has feature called “Office web app”, I have already explained about office web app in this post: http://sanketinfo.blogspot.com/2011/07/how-to-install-office-web-app-for.html
With Office web app, we can open Microsoft application in browser; still there are some features which are not available in browser view. Here is link which talks about differences for Excel 2010 in excel client and in the browser: http://office.microsoft.com/en-us/excel-help/differences-between-using-a-workbook-in-the-browser-and-in-excel-HA010369179.aspx
