I thought it was quite well explained but obviously not.
A guest has limited abilities, they can do gedmatching but not importing, they can adopt orphans but they can only edit their own profile.
If a guest volunteeres they are saying they want to contribute and work independantly and a greeter can confirm them as a family member. If they are not volunteering to help but a family member or friend wants to work with them then they can be confirmed as family members without volunteering, all this means is they will not have a volunteer badge and the person who confirmed them is willing to work with them on close family genealogy. Either way the family members has more editing abilities, they can edit profiles if they are on the trusted list and can manually add profiles but not gedcom imports.
A family member can 'sign' the honor code and become a genealogist which gives them the ability to edit any open profile even if they are not on the TL and they can import gedcoms.
The volunteer badge is just an indicator of how the member joined wikitree, people without the volunteer badge have usually joined by being invited by a family member or friend.
The honor code makes life simpler for genealogists who work on older profiles, often not in their direct line, not signing means you have to get on the TL to add information. Currently anyone other than guests can add profiles though there are discussions to change the system where only qualified genealogists will be able to add or edit older profiles.