It is possible to download YouTube videos to your PC. I.e. if you particularly like something on YouTube but you also think that at some stage it may be deleted you may wish to download it to your PC where you can play it for ever. There are 3 possible ways to download.

1) Join YouTube Premium service, but it is a standard monthly payment, expensive if you only need to occasionally do any downloading.
2) Buy download software but again it is expensive if you only need to occasionally do any downloading and you also pay for any improved version.
3) Get free downloading software or the free version of the otherwise paid for software that is offered. This is what I have done. If it is the free version of the otherwise paid for software it is perfectly satisfactory for me. In the extremely unlikely event of me upgrading to the paid for version this would enable the downloading of several videos at once. I do not need that facility. In the free versions of paid for software there can be a limit to the number of videos that you can download per day but it is at least 3 per day in all that I have seen, usually 5 or more per day. That is perfectly adequate for me.

I use Anvsoft's Any Video Converter. As well as being a converter it is also a downloader.
https://www.anvsoft.com/any-video-converter-free.html
If you scroll down that page you will see that it is quite versatile, especially in terms of what it can read and write.