The Transformers are a species of sentient, living mechanical beings (mostly) originating from the distant machine world of Cybertron. The stories of their lives, their histories, and most especially their wars have been chronicled across many different continuities in the vast multiverse.
The designation "Transformer" stems from the species' generally-shared ability to "transform,", to change their bodies at will, rearranging their component parts from a robotic primary mode (usually, but not always, humanoid) into an alternate form; generally vehicles, weapons, machinery, or animals. In some continuities this ability to transform is innate to all members of the species, in others it was a wartime innovation that was adopted by most, but not all, of the populace.
Although "Transformer" is the most common term for these beings, there are others, mainly "Cybertron" as a reference to any being whose origin traces back to the planet in question (the adjective form being the more frequently used "Cybertronian").
In the Star Wars Universe most of the Transformers are at the size of 1.85.
Also the Cybertronians can call for a special ability called a Cyber Key Power which makes them more formidable in combat.
Stealth force mode makes special weapons activated around a robot in vehicle mode which is pretty fast, more armor and firepower.
In Darth Grievous's evil vision of the future all the transformers including the Autobots and the Decepticons were exterminated by Darth Grievous except for the Demon Generals and the Sith transformers during the Autobots last stand against the Sith.