A tribe is considered a group of players/friends who unite together to preform various tasks around a server. One of the most common activities a tribe will do is set up a base. These bases can be built to stand for a very long time, or be poorly built and be burnt in an instant. Another activity that is a little less common is raiding, where the tribe will build a boat (usually a Frigate), and travel around the server, burning, stealing, and killing anyone and everything they find.
It's usually best to have around 4 other people in your tribe, but more can be better if everyone knows what they're doing. The best way to start up is to send one or two people out to recover different ores and metals in order to build better tools and protection. While whoever is left can build walls, mills, garden, cook etc.. Raiding is usually done later on in the game once everyone has strong equipment.
One other activity that tribes can preform is trading and selling various items to other players, though this has become very rare.
Stages of tribe development:
1st stage:The tribe is consisted only of newspawns which are together only because they spawned at the same place.Sometimes a player which settled here will be in the tribe providing most if not all food for the group.Will fall apart under a raid or when one of the tribesmen gains a weapon and kills his partners.
2nd stage:The tribe has built a mill and/or cotton gin and probably imported some food.They are often consisted of 2 to 3 people and aren't very rich unless near a rich source of ores and will probably fall apart under a raid leaving their small possessions to the raider.
3rd stage:The tribe has gotten big and have built some walls to prevent attacks.At this point there is at least one expert player with a Mithril sword and he forms the backbone of the tribe.Most often found on Cliff Island as its easy to defend and Mainland due to its riches.They have probably moved away from eating apples and berries and are baking pies and banana bread.
4th stage:The tribe has gotten so big that they are overpopulating their island and are in need of new space.At this point they can either fall apart as one of them gets greedy and steals from the granaries knowing that they wont find him so the tribe falls apart in a civil war or they will colonise another island and stay united.Most members have Mithril Swords and their biggest threat is internal strife and not raiders.
5th stage:The tribe has built a stone castle,probably owns a frigate or 2 and if powerful enough the only real tribe in the server since they can easily destroy every other tribe in an instant.This stage of development is reached very rarely and if reached at all it is probably in the Mainland due to its riches and the Mithril sources.
This section contains all known major tribes that play often.