Types of notes for a zettelkasten
1.Fleeting notes, which are only reminders of information, can be written in any kind of way and will end up in the trash within a day or two.
2.Permanent notes, which will never be thrown away and contain the necessary information in themselves in a permanently understandable way. They are always stored in the same way in the same place, either in the reference system or, written as if for print, in the slip-box.
3.Project notes, which are only relevant to one particular project. They are kept within a project-specific folder and can be discarded or archived after the project is finished.
Sources
Book - How to take smart notes