MORK IS BEZT AT SNEAKIN'ND SMASHIN WAAAAAAAAGH!!!
- The Shoutings of Mork on how 'Kunning' he is
Mork is one of the two Ork gods. He is more cunning but still brutal, while Gork is more brutal but still cunning. The core "difference" between them is that Mork will hit you when you aren't looking, while Gork will hit you harder when you are.
Prior to 7th edition, Orks had no idea which god was Mork and which god was Gork (and debates were just another excuse to fight each other). This was eventually dropped because it was super awkward to write. Most likely the Prophet of Gork and Mork laid down his head-canon, and the other Orks figured he was big enough to close the matter.
And before you ask, no, he does not say "nanu-nanu" or "shazbot".
As mentioned above, Mork is the Ork God for sheer cunning and determination. Some may debate that the ork Gods can compete with the Chaos Gods when talking about cunningness or power, but there is no way of knowing for sure. As the Warp's nature is ever-changing and spontaneous, the might of a certain god is never set in place. Although, there is a fact that each race's feelings are represented by an entity in the Warp and as the ork population and crusades grow in number, so does the might of Gork and Mork. In the long run, in a sense, he could arguably be one of the most powerful entities in the warp along with his twin Gork and the Chaos Gods.
In contrast to his twin Gork, Mork often favors (and in return is favored by) those of
any some intellectual ability, meaning that Big Meks, Flashgitz or any other Orks who actually use their brains once in a while are often a prime candidate for Mork's favor. Hence, though Gork may be more physically powerful of the two, Mork is arguably the more intelligent and wise of the twins.
From what can be determined, given what little (if any) history is available on the Orks, both Gork and Mork came into existence upon the Orks' creation when they inadvertently started channeling their essence (and wanton violence) into their gestalt field, similar to that of the Eldar; however the Orks' gods often like to get a bit more 'personal' with their subjects i.e. will offer cosmic aid to whoever is chanting their names long enough and if they decide they are worthy enough of their aid; if they are considered worthy, then woe to any forces opposing the tsunami of green people.]] Although they are both idolized upon, the Orks often have no idea who they are directly praying to resulting in much lulz if a Weirdboy praying for Gork's space foot to crush the enemy summons Mork instead, who makes his head explode for mistaking their identities (not that they care THAT much).
The only distinction that can be made between the two is that Gork is the more favored of the two gods for the more common greenskins, as he is the manifestation of power and might for the Orks, while Mork is more favored towards Orks that possess a sheer level of intellect and cunning such as BigMeks, Gretchins, Flashgitz and other Oddboyz. Whatever is the case, both are rumored to be more powerful than Khorne, due to the sheer psychic might of the Orks, and may actually have the power to snap Khorne like some sissy daemonette.
Mirroring the Orks as a faction themselves, Gork and Mork united could probably overpower any other god. Also much like the Ork race, they fight each between themselves as much as external threats, much to the galaxy's relief. Fundamentally, this is the reason for the Orks to venerate twin gods. Though mild distinctions can be drawn, in practice Gork and Mork are identical. The reason there must be two is that Orks prize the glory of combat above all things. Why have two gods where one would suffice? So they can fight.
Although no one has the faintest idea on what these twin gods may truly look like, they can at least be interpreted through the various designs of the BigMek's Stompas and Gargants, which are noted to be effigies of the two gods.