Automatic Volume

Since I’m beginner in using audacity, I didn’t know what to search for. I didn’t even know what to name this topic!
So, if this is a duplicate question, I apologize sincerely.
I’m going to create a podcast with audacity.
I want to put music in the background, but, I want to do this: when I speak, the volume of the background music goes down automatically, and vice versa, when I don’t speak, the volume comes back to normal.
I don’t know how to do this!
I’d be so grateful if you give me a step-by-step guide.

See Auto Duck - Audacity Manual .