What is the difference between dual trace oscilloscope and dual beam oscilloscope?

hello!

dual beam oscilloscope has 2 filament in crt tube that made 2 independ beam.

but tahe dual trace oscope has 1 beam and made 2 channel indicate on screen by high frquency switcher. it mean,one beam alterative swtch between ch1 and ch2 to indicate 2 channel waveform.

excuse me for bad english knowledge!!

bye