DM-Verity explanation


Hello Everyone,
I am new in the root and ROM cosmos and there are a few things I am curious about.
I´ve seen a few different phones, which need the no-verity-opt… , so I guess it´s not phone specific.
When it´s installed, there will not be a warning in twrp that your system is encryptet.

  1. So does it decrypt your system?
  2. Why is opt in the file name, does mean optional?
  3. Do we format data before flashing no-verity-opt…, so that there won´t be an encryption. And because the no-verity-opt… makes encryption optional, data is decryptet, at least for now?
    4.So when I install a ROM afterwards, let´s say lineageOS, does it stay decrypted or do ROMs start encrypting the system again?
  4. Do I have to flash no-verity-opt… for every ROM or is it enough to do it once? Does it any harm to do it every time I flash another Rom?

I would be very thankful for any answer!
Ps: I am sorry for my english, but I am from germany and not that familliar with your language.