Permissions explanation

[Lee]

I'm trying to fix permissions for a Worpdress application on a plesk server. It's a manual install, not through the Applications manager. I have five options for file permissions:

- Administrators
- Plesk Domain User
- Plesk IIS Anonymous Account (UISR_myadminuser)
- Default Plesk application pool user (IWAM_plesk(default))
- SYSTEM

Can anyone explain what each of these mean and the ideal permissions I should set for all file/directories?