Do the mixing and automation, are they one and same thing? If no, what is a difference? And are they both taking place only then, when the song is ready?

Automation can [optionally] be a part of mixing. Mixing is the art of balancing and blending all the tracks in an arrangement so everything is heard clearly; mixing also involves using processing and effects to improve and enhance the sound. Automation allows the mixer to record changes in level, pan, and processor settings over the course of the song, when static levels or effect settings don't work for the entire length of the song. In the attached video, check out video #33 on Automation in GB.

I don't understand automation video. In the beginning, he moves playhead to the position. What kind of position? It seems like a random position, as then he puts to the volume line 2 automation points, and first of them is 13 millimetres far away from playhead.. not that the same point as playhead. So I don't understand, where to put my playhead exactly? And if I try to put another automation point, it can't appears on the line.. But I still have by default a point in the beginning of the line (as he has, first by default and 2 by him and I have default and 1 by me), and my volume rises or lowers between the beginning of the line (default point) and my first point I put. Why I can't put the second point as he did (he put 2 points by himself) and what I have to do with playhead, to what position to move it.. ?

Forget about the position of the playhead, it doesn't make any difference -- you add Automation moves wherever you feel the need to change a setting. For example, if the volume of, say, the vocal track needs to be adjusted for one line, you'd add volume Automation points there, adjusting the level just during that line and going back to the original level for the next line.

I only can add one, the first automation point, but not the others. Why? I'm adding them, clicking once on the line. On the screenshot, you have added 4 points, as I see...

You can click once to add the first Automation point, but then you have to double-click to add the others.

Yes, that's correct. Thanks! I looked at the automation video again. There are many choices, like pan, echo, pedalboard etc. But he only shows how to use a pan and nothing more. He used a pan in audio file, I used it in software instrument, no difference.. And what is a pan? Do the any of automations are for software instruments, and others for real instruments? Can you tell me, which ones are software instruments ones? And among loops, there are also audio loops, I can use. Do the automation effects to the loops, too? Do all automation choices are always as a line with points? Like volume, pan.. ?

You can Automate any of the parameters in those lists, on any kind of track. If you think a particular aspect of the mix needs to change over the course of a song, then Automate that parameter; if not, then there's no need to use Automation -- don't feel that you have to use it just because it's there.

I didn't find a video about automation parameters mid freq and low cut related to vocal, so I tried it on gb myself. In low cut, I noticed that my voice sound maybe a bit lower. But who knows, maybe I just sang so. Mid freq hasn't effect at all. For what are they exactly? And I make a curve in low cut and then I wanted to use the same curve with mid freq, but in changing of parameters the low cut's curve also disappeared with that low cut. How can I use the same curve, just not typing again the same thing, in another parameter?

For a general tutorial about EQ, watch this video [and the following videos -- 8, 9, 10, 11, 12, 13].. https://www.macprovideo.com/video/audio-processing-basics/8-8-eq-basics?afid=E470KLQ7r9