History: What are ratio and depth in reverb?

What are ratio and depth in reverb?

• Ratio and depth will impact the number and intensity of the reflections.
  Correct!
• Ratio and depth are the initial, loudest reverberations.
  That is early reflections.
• Ratio and depth is the amount of time between the original source and the start of reverberation.
  That is predelay.
• Ratio and depth sets how long the reverberation will sound for.
  That is decay time.