OpenOffice.org is a multiplatform and multilingual office suite and an open-source project. Compatible with all other major office suites, the product is free to download, use, and distribute.
OpenOffice is as good as Microsoft Office which can cost in excess of £300 for the functionality provided free in OpenOffice. Files made in Microsoft office can be opened in OpenOffice and OpenOffice can save files in a format that can be opened with Microsoft Office with a small setting change.