The original Orcs that inhabited the Gong-Goi (Orc."Goblin-Town") were be split into two different groups. The Lakog-kadaf (Or."twisted Neck"), armored, brute Greater Orcs of the Orc-stronghold were Mountain Orcs hailing from Gundabad and its vassals, descendants of Morgoth's Warrior-Orcs. The other- and more ubiquitous -group , the Hangrishúrz (Or."Bloody Moon"), were Deep-Orcs, small and degenerated Goblins hailing from the Underdeeps descending from the Snaga-caste of Utumno. In the Second Age these originally-wild Orcs were conquered by the Sorrushki (Or."crow-feeders"), Greater Orcs from Barad-dûr who had been sent by Sauron to take control and fortify the passes over the Misty Mountains such as the High-Pass and the Old Pass. These lackeys of Mordor soon rose in the local Orcish hierarchy and asserted themselves as iron-fisted the rulers of the indigenous goblin-tribes and ordered the tunneling of the vast under-mountain Orc-hive known as Goblin-Town.
The clans of Goblin-Town were nonetheless numberless despite their devisions and often blended to give the illusion of a sole faction, and indeed through persistent and endless work and the brutal rule of the Greater Orcs, they collectively forged a great tribal federation known as the Uruk-Tarkhnarb ("Orc. "Orcs of Many Wounds"). The tribal federation’s traditional ruler was the Durba-Hai, or Great Goblin, and usually an individual descending from the minor bloodline of Ogslap, a descendant of Lokkak the Boldog.
The Movie Trilogy shows the Orcs of Goblin-Gate as degenerated and primitively equipped Lesser Orcs, much similar and probably related to the Moria Goblins and the Snagas of Isengard and Mordor. Only a few of these Orcs appear of greater statue, among them the grotesque Great Goblin. While these goblins are not further described in the Book beyond simply being “big” and “ugly,” it can be assumed that the same physical variation present in other Orcs in Tolkien’s works was present here as well. It can be assumed, based on the appearances of Greater Orcs of the kind from Gundabad in the movies as well, that Orcs of that type were also present at Goblin-Gate, where they served as the goblins in armor described in the book.