Dual radio, as the name implies, means two radios. One radio operates on the 2.4 GHz and the other on the 5 GHz spectrum. "Dual band" access points can operate on both spectrums although not necessarily at the same time.

It's important to be prepared for the upcoming tri-band access points, which will have THREE radios that operate each on the 2.4, 5, and 6 GHz spectrums.