All documents in OpenOffice.org (OOo) are based on templates. However, Impress is a little different from other OOo components, in that it starts with the Presentation Wizard unless you have elected to turn the Wizard off.
When you choose File > New > Presentation from the menu bar, if the Presentation Wizard is active, the Wizard offers several choices for a new presentation, one of which is From template.
If you have turned the Presentation Wizard off, when you start a new presentation by choosing File > New > Presentation from the menu bar, OOo uses the default presentation template. If you have not defined your own default template, OOo uses an inbuilt blank template supplied with the program.