LibreOffice is a free software package that offers programs that are similar to Microsoft Office including a spreadsheet and database management system. Open Office can read and write most Microsoft Office files. It also enables use of a modern open standard, the OpenDocument Format (ODF).
LibreOffice branched out from OpenOffice and is built on the original OpenOffice code base. The two packages are very similar, although there is currently more activity surrounding the development of LibreOffice.