How to create metadata?

To edit own metadata via browser in plex is super decent. I did that for a good bunch for my pro wrestling and sport collection. Then I had to resetup my plex server and of course, the metadata was gone.
Somebody told me I can put the video file in a folder, put a poster file into it and a text file with the metadata like title, release year, etc. that i can use it after reinstalls.

Can somebody give me a hand on that to start?

If you have mp4 and/or m4v files, you can embed most of the data directly into the files.

For all other file formats you must make use of Kodi-compatible .nfo files.

Thanks man, gonna check the links and hope to find what I’m looking for!