LibreOffice published by the Document Foundation is a complete free office suite. It may not be as popular as other high priced office suites, but in terms of features it can compete very well. The best part is that it is completely free.
When you start the program, a menu will appear. This allows you to select what program to use. The choices are Writer, Math, Impress, Draw, Base and Calc. Impress is a presentation program while Base is used for database integration.