The KOffice is an integrated Office suite for KDE, the
K Desktop Environment.
KOffice currently includes KSpread, KPresenter, KChart, KImage, KIllustrator, KFormula and KWord.
KSpread is a spreadsheet, KPresenter is a presentation application, KIllustrator is a vector drawing program,
KWord is a WordPerfect-like wordprocessor, KChart draws charts and diagramms, KFormula is a formel editor and
KImage is a simple image viewer.
Of course the KOffice is, as the whole KDE project, a free project which is released under the GNU GPL.
Look at the description of the main KDE Category for more information about KDE.