I don't understand. What mean overlapping notes and how can I'll have them on a different track? In different tracks I have different regions, that's clear. And thus I can avoid overlapping regions, it is also clear. So then is no sense for overlapping regions at all, right? But you write better to have overlapping notes on a different track. How to understand that sentence? As notes are existing only inside the region, right? So how can I have overlapping notes and avoid overlapping regions (your last post) ? I don't understand.

Overlapping just means notes that happen at the same time. If you simply record normally, and don't use the Command key when moving Regions around, you shouldn't have any overlapping Regions *on the same track*. Of course it's normal to have notes that occur at the same time *in different Regions* *on different tracks*, and that's fine -- that's what I meant.

So overlapping regions have no sense, as better to have overlapping notes on different tracks anyway.. ? And overlapping notes you mean here just notes the same time but on different tracks, as just a normal song is ( one melody, multiple tracks ), right?

Yes, I would suggest you avoid overlapping Regions on the same track, and use multiple tracks, just as you said.

I understand overlapping regions occur when I use the command key when moving regions around. But you wrote, they occur also with trim tool. Does it mean that if I stretch a region with trim tool, then after that I'll get overlapping regions? Or have I use trim tool + command key all together, to get overlapping regions?

You have to use the Trim Tool + Command to make a Region overlap another Region.

Is it common to use the overlapping regions, when making music, in garageband, or at all in any DAWs? I mean if I want to make pop music or instrumental music, how often in these songs the overlapping regions are exist? Or can I make a good (quality) pop song without the overlapping regions? I mean, are the overlapping regions necessary?

Whether or not any Regions need to overlap in an arrangement is entirely dependent on the musical parts you create. It's impossible to say if there might be overlapping Regions in certain styles of music, or in certain DAWs -- a Region overlap is not a feature or a process that makes your music better or worse. As I said, if you have a musical reason to overlap Regions, then do it; if you don't have a musical reason to overlap Regions then don't. If you can't think of a musical reason to overlap Regions, then don't worry about it -- you don't need them, they serve no intrinsic purpose. I reiterate my suggestion from a previous post -- avoid overlapping Regions and don't overthink it.

Well, for any case, as double-click I tried this one - I clicked quickly 2 clicks by each other, and got regions longer. What is it, for what is it good, and is it any shortcut.. ? For what I need these longer regions.. ? https://youtu.be/7IuKnzK2yuE

I don't see Regions getting longer in the video -- other than the zoom (track height) changing I don't see anything happening there at all.