There’s a plethora of DVD formats: DVD-R, DVD+R, DVD-RW, double-sided, dual layer… Unless you have a new-ish Mac, which can handle almost anything you throw at it, how can you tell which DVD formats your Mac can write to?
Choose > About This Mac and click the More Info button. In Profiler (why don’t they just rename that button to “Profiler”?), click Hardware in the Contents column to expand it, and then click Disc Burning. The right pane lists the CD and DVD write formats that you can use.