TL;DR
The best summary is given by Rats in this Topic http://tamriel-rebuilt.org/old_forum/viewtopic.php?t=24673
The Fighters Guild in Morrowind.
Even though the fighters guild has been met with opposition, it has gained a significant foothold in the province. House Hlaalu and Dark Elves who don't mind the Empire see the fighters guild as useful business partner, whereas conservative Dunmer(Indoril for example) are more hostile against the idea of the fighters guild, seeing it as foreign occupation.
The current situation
The fighters guild is faced with collapse, the guild has managed well in the province, but the reasons behind their succes are laid bare. Though officially controlled by the guild leader in Cyrodiil and the Imperial Council, the guild is gradually taken over/influenced by the Camonna Tong.
The guild is split in half: those whom are controlled by the Camonna Tong and those who aren't. These forces will have to collide eventually.
Not only the Tong's corruption is a threat, the current leader of the guild: Grandmaster Joccathe of Bladed-Hymnals, has left the guilds headquarters, in search for medition. She has become more doubtful about the presence of the guild in Morrowind, thinking that, maybe, Morrowind would be better of without the Fighters Guild. Her dwelling on the ancient roots and ethics of the fighters guild, makes her blind to what the Tong's corruption does to the guild.
The player's plot.
The player's role is to uncover the truth behind the corruption and use this gained knowledge as the player sees fit. The player Chooses between two paths and decides for himself which one to take.
Relation to the Thieves Guild.
When choosing one of the options, the choice would lead to a open conflict with the Thieves Guild. Because of this, the player would be required to kill key members of the Thieves Guild, making the Thieves Guild questline incompletable.
