Oi, ya git! Get in, wese gonna have some fun!
Trukks are the very basic vehicles used by da Orks in Warhammer 40,000. While GW emphasizes that it's a specific vehicle, in reality it can be any Ork vehicle smaller than a battlewagon. It is by far the most common Ork vehicle, used by every force from the most basic Boy to Warbosses and Goffz to Evil Sunz. Most commonly they're the barebones chassis of some Looted vehicle, an engine, and whatever scraps of metal or weapons are bolted onto it. Usually they're owned by a Nob and used to carry a mob of Boyz to the front.
If a Mek (or any Ork or neckbeard in general) gets their grubby mits on the burned-out shell of a Rhino, Ghost Ark, or any kind of small transport, it will most likely be kitbashed into a Trukk of some variety. Given the Ork fluff, simple rules in terms of crunch, and the lenient "Counts As" rules at most tournaments when it comes to Ork vehicles, the Trukk has the most variety and customization potential out of any vehicle (and maybe any model) in the entire game.
Regardless, it's not a Munky. Not even the Orks are so dim to confuse it for one.
The Trukk can be taken as a Dedicated Transport for most Ork infantry units. For a 12 man Open-Topped transport with T6, 10 wounds, and a 4+ save, it is
a steal at 30 points pretty reasonably priced at 59 points, as of 8th edition. The vehicle comes with a single Big Shoota by default, but you can also slap a Wreckin' Ball and/or a Grabbin' Klaw for some extra melee crumpin', or take a Stikkbomb Chukka to give it a little bit more ranged firepower at 12" or less. Of course, since it is Open-Topped the Orks riding inside can all shoot out as well. Unfortunately, Trukks can now only use their boarding planks by paying to do so through the Boarding Action stratagem. It should be noted that like a number of other Ork vehicles, Trukks only hit in melee on a 5+. Despite this Trukks are commonly used to charge first and tie up a unit in melee so that your Boyz don't get picked apart by Overwatch fire.
As vehicles go Trukks are not particularly resilient, so don't expect them to last long under heavy fire. That being said, they do have a trick up their sleeve in the form of the hilarious rule Ramshackle, which means that any time a Trukk is hit with a damage characteristic of more than 1, on D6 roll of a 6 that damage is reduced to 1 point. Laugh your ass off as your opponent's Lascannon takes off nothing more than a piece of sheet metal.
Overall Trukks have limited ranged firepower that is mitigated by their Open-Topped ability, and they can be upgraded to be mildly useful in close combat. Spare the upgrades you won't need, though, as Trukks are meant to be cheap, expendable delivery systems for your Boyz and nothing more.
From 1997-2007 Ork players had to content themselves with the old Ork Wartrukk, a tiny and inadequate model which was a Gorkamorka leftover.
The ancient ancestor of all subsequent Trukks was the Battlewagon, which GW released as a kit in 1990 (no direct relation to the current Battlewagon).