Microsoft Office Alternative

Microsoft office is a product of Microsoft. It has business applications like Word, Access, Excel, power point etc.
http://office.microsoft.com/en-us/default.aspx

This runs on windows platform and is a commercial product, you may find price information at http://office.microsoft.com/en-us/products/FX101211561033.aspx

There is an open source alternative available named "OpenOffice".
http://www.openoffice.org/

This runs on windows, linux, sun solaris and mac operating systems. It has another specific version for MAC OS called "neooffice".
http://www.neooffice.org/neojava/en/index.php