Black Speech is one of the fictional languages invented by J. R. R. Tolkien for his “The Lord of the Rings” trilogy and the legendarium surrounding it.
Canonical Black Speech is divided into Classical Black Speech invented by Sauron and Debased Black Speech, a collective name for various dialects and languages spoken by Orcs in the Third Age. While some words of Black Speech were borrowed from languages of Orcs of the First Age (like suffix “-hai” and the name “Gothmog”), 1st Age Orcish is not a Black Speech, and judging by various personal names, could be called a “debased” Sindarin. Anthony Appleyard suggested term “Angband Orkish”.
In internal history, Black Speech is a constructed language invented by Sauron during Dark Years of the Second Age for his servants. Helge Kåre Fauskanger, author of Ardalambion site, called it “Sauron's Esperanto”. The only example of Classical Black Speech is the Ring Inscription.
It is said that the Black Speech was devised by Sauron in the Dark Years, and that he had desired to make it the language of all those that served him, but he failed in that purpose. From the Black Speech, however, were derived many of the words that were in the Third Age wide-spread among the Orcs1).
but after the first overthrow of Sauron this language in its ancient form was forgotten by all but the Nazgûl. When Sauron arose again, it became once more the language of Barad-dûr and of the captains of Mordor.
Only Nazgûl remember it and probably a newly-bred (in the 3rd Age) kind of sun-tolerable trolls called “Olog-hai”, however those spoke a little:
They spoke little, and the only tongue that they knew was the Black Speech of Barad-dûr.
The men under Sauron's influence probably knew Black Speech too, but never used it among themselves, only in communication with Sauron's forces:
The Black Speech was used only in Mordor…. It was never used willingly by any other people (Letter 144 to Naomi Mitchison)
Debased Black Speech varied from Black Speech with bad grammar (like Orc-curse) near Mordor to basically Westron (also with bad grammar) with occasional Black Speech words in northern regions like Misty Mountains and Moria. Orcs of different tribes spoke Westron (Common Speech) when met together to avoid misunderstanding and confusion between different versions of Black Speech.
So it was that in the Third Age Orcs used for communication between breed and breed the Westron tongue; and many indeed of the older tribes, such as those that still lingered in the North and in the Misty Mountains, had long used the Westron as their native language, though in such a fashion as to make it hardly less unlovely than Orkish.
To Pippin’s surprise he found that much of the talk was intelligible; many of the Orcs were using ordinary language. Apparently the members of two or three quite different tribes were present, and they could not understand one another’s orc-speech. (LOTR II, Book Three, Chapter III: The Uruk-hai)
Neo Black Speech is a collective name for different fan's attempts to reconstruct Black Speech, including Nûrlâm described here. Each version is called a “dialect”. Their authors provide a parallel between their own versions and situation with various Orcish jargons, when orcs of different tribes could not understand each other. So, all Neo Black Speech dialects belong to Debased Black Speech but are not canonical, including Nûrlâm.