In Bluestep there are two types of permission groups. There are the user created ones used on the Organization Admin's User Groups page, and there are the default system ones. The default permission groups will show up on a form with a grayed out trash can and most will default to 'No Access.' Here is a brief overview of what they do and where it's safe to use them:

Everyone: Gives access to anyone on the internet. Should only be used for information that the facility is okay with people not involved with the facility in any way to view.

Registered Users: Gives access to anyone with a username/password to the site. This can include former staff, so it's usually limited to places where further permissions will limit access (for instance, merge reports will frequently be set to let Registered Users access, then be displayed on fields or other places that have more restrictive permissions), or the information is non-specific. This security group is usually restricted to Reader, except in cases like fields used for date ranges.

Relate Creator: This gives special access to whoever created a specific entry. This would be used if the person who hit the New Entry button should then be the only one allowed to edit certain fields on it or to delete the entry.

Relate Licensees/Unit Admins: These groups are the only ones that default to Editor when creating a form. Most orgs do not have any users that belong to either group, as usually organization administrators are used instead which supersedes all permissions. 

Relate Self: Gives access to the person whose record is being looked at. For instance, a staff could log in and Relate Self would let them make changes to their own information without giving them access to view or change the same information on another staff's record. For residents, it's most often used with the Family Connect so family can log in with a resident's record and only view information that pertains to that resident.