What is the difference between this disks (0 and 1) on my Mac?
The primary difference is that disk0 is your physical disk and it contains three things: GPT header table, EFI partition (that does not share space with the other partition disk0s2), APFS Container (that does not share space with the other partition disk0s1).

disk1 is how the APFS container is shared out to store other files that all share free space.



The details of APFS are on WWDC 2016 where this was introduced. The image above is from this developer documentation - https://developer.apple.com/documentation/foundation/file_system/about_apple_file_system

Since you are on Mojave or older, you don't need to worry about all the Catalina changes (yet) but here is the best listing of technical details on how this shared space using APFS containers will work for macOS in the future:


https://eclecticlight.co/2019/10/11/macos-catalina-boot-volume-layout-revised-for-10-15-release/


To return to your question, the only place you store files in in Macintosh HD - disk1s1, the other synthesized volumes VM, PreBoot, Recovery are for the system to store things it rebuilds and you don't need to back up as part of your normal use of a computer.