Short answers, pulled from the story.
The Black Speech is a fictional language forged by the Dark Lord Sauron to bind his armies in Mordor under one rule. It serves as the sole language for creatures serving him, though no other people spoke it willingly.
By the end of the Third Age most Orcs communicated using debased Westron instead of pure Black Speech. One Orc described another's speech as almost as hideous as his own native tongue before this shift occurred.
A couplet written on the One Ring stands as the only complete text of pure Black Speech. It appears in Elvish Tengwar script with decorative flourishes added by Tolkien himself.
David Salo expanded limited vocabulary for Peter Jackson's film trilogy using invented phrases based on existing fragments. He created two new lines that translate to no life in coldness and death here in void while borrowing words like ash from the original verse.
J.R.R. Tolkien intended the Black Speech to sound rough and guttural throughout its structure to create an unpleasant effect for listeners. The language contains 63% consonants far higher than Elvish samples at 52% or 55% to mimic speech affected by aggressive emotions.