Not a problem, I enjoy talking about this, the paragraphs just flow, you know?
I can TRY and explain the "very important reason" but before, let me ask you a few of my own:
-Do you know what frequencies are?
-How good are you with Maths?
-How familiar are you with the principle of decibels?
-Do you have a good ear?
Also: an external amp is any and all device used to amplify your song AFTER you've encoded it. The big box with the VOLUME dial between your speakers? That would most likely be your external amp.
Entertainment? Stories and laughter? Sure, why not. Not what I had in mind though

You also mentioned you needed a topic to discuss my music: this one would do just fine!