OpenOffice.orgopen source office software. The ".org" part of the name is there because of its links with the Internet and because the words "open" and "office" are common and the developers do not want to get in trouble with trademark issues. It is often called "OOo" for short. It is based on the older Star Office software that was opened by Sun Microsystems. You can use OOo on Apple OSX, FreeBSD, Linux, Microsoft Windows and Solaris.
There several applications in OOo. Writer for writing letters and documents, Calc for creating spreadsheets, Impress for presenting information, Math for maths formulas and Draw for drawing.