Earth-82
The Transformers are a species of sentient, living robotic 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.
While this species is commonly known throughout the galaxy as "Transformers", the technical term for these beings is Cybertronians, which they generally use to refer to themselves. Other, less-frequently used terms to refer to beings from Cybertron include Cybertronic or simply Cybertron.

Autobots

The Autobots are one of the primary factions in the Transformers mythos. They usually find themselves defending both their own race and other species against the Decepticons and upholding justice and freedom throughout the galaxy.
A generally heroic, honorable group, they tend to be dedicated to peace, and feel a need to protect other races from the Decepticons. As a result, they are usually Transformers who change into non-combat oriented alternate modes such as domestic vehicles, cars, trucks, or rescue vehicles. This is not always the case, however, as their ranks certainly contain ne'er-do-wells, malcontents, and unsavory types, and the necessities of war have led many to adopt more combat-oriented alternate forms. While the Autobots have usually found themselves outnumbered by the Decepticons, the Autobots have always had home-field advantage, having not only the humans' military support, but also having more places on Earth to fall back on, while the Decepticons are entirely unwelcome on Earth.
Key concepts that repeat throughout most continuities are the use of the name Prime (or a variation thereof) to denote Autobot leadership, and the existence of an artifact of great life-giving power, usually referred to as a "Matrix", traditionally held by their leader.
The collective noun for Autobots is an "exaltation".

Optimus Prime Orion Pax	Prowl	Ironhide	Jazz	Jetfire

Bluestreak	Silverstreak	Smokescreen	Sideswipe	Sunstreaker

Tracks	Mirage	Sandstorm	Skids	Hound

Wheeljack	Perceptor	Ratchet	Inferno	Red Alert

Trailbreaker	Hoist	Grapple	Bumblebee	Beachcomber

Brawn	Cliffjumper	Gears	Huffer	Outback

Pipes	Swerve	Windcharger	Powerglide	Sea Spray

Cosmos Interplanetary Transport	Warpath Demolitions Specialist	Omega Supreme Heavy Assault Station

Espionage Team

Blaster	Eject	Rewind	Ramhorn	Steeljaw

Dinobots

Grimlock	Slag	Sludge	Snarl	Swoop

Aerialbots

Skybolt	Fireflight	Skydive	Air Raid	Slingshot

Superion

Protectobots

Hotspot	Blades	First-Aid	Groove	Streetwise

Defensor

Autobot Cybertron Forces

Ultra Magnus	Elita One	Springer	Kup	Arcee

Alpha Bravo	Blurr	Broadside	Bumper	Chromia

Cloudraker	Fastlane	Firestar	Glyph	Greenlight

Hot Rod	Lancer	Moonracer	Roadbuster	Sky-Lynx

Topspin	Twin Twist	Vibes	Whirl	Sentinel Prime Deceased.

Zeta Prime Deceased.

Technobots

Scattershot	Afterburner	Lightspeed	Nosecone	Strafe

Computron

Maximals

Arising from the ashes of the Great War, the Maximals are the descendants (at least in part) of the Autobots, controlling Cybertron under the Pax Cybertronia. The Maximals and their counterpart race the Predacons both owe their origins to the Great Upgrade, which provided the downsized, fuel-efficient bodies that became the hallmark of the successor factions.
In many ways, the Maximals share traits with their Autobot ancestors; primarily a "civilian" race, the Maximals are committed to upholding the peaceful, democratic values of their forebears. All this said, they aren't perfect: they still have their jerks, and Maximal science has occasionally resulted in the odd unethical scientific horrors.
The most distinctive factor of both Maximal and Predacon physiology is their development of pseudo-organic beast modes, allowing both sides to adopt alternate modes that blend in seamlessly with the organic lifeforms found elsewhere in the universe. This technology, an offshoot of earlier Pretender tech, sheathes a beast mode in an artificial organic skin, integrating its natural instincts directly into the Maximal form.
When Maximals take on beast modes, they tend to select mammals, birds or fish, although this is not a hard-and-fast rule. Occasionally, Maximals might choose to become insects, reptiles, or dinosaurs.
The Maximal activation code is "Maximize".

Optimus Primal	Rhinox	Cheetor	Rattrap	Dinobot

Airrazor	Blackarachnia	Silverbolt	Tigatron	Depth Charge

Decepticons

The Decepticons are one of the primary factions in the Transformers mythos. They are typically concerned with such things as conquering Cybertron, defeating the Autobots, amassing large quantities of energon, developing powerful weaponry, and beating people up. Not necessarily in that order.
Unlike the Autobots, whose leader is a Prime bearing a Matrix, the Decepticons are led by the most powerful of their ranks. This tends to cause some conflict, given how generally every Decepticon thinks that they're the most powerful. Also, the Decepticons are not exactly the most compassionate beings in the universe, but not all fight for greed. More than a few have a sense of honor, while others believe that Cybertron would be better protected by aggressive expansion. Ultimately, the Decepticons desire to protect their homeworld, even if it is at the expense of others. Usually.

Megatron Decepticon Leader	Octane	Astrotrain	Blitzwing	Barricade

Knock Out Medic	Bombshell	Kickback	Shrapnel	Nightbird

Vehicon Drone Ground Commander	Vehicon Drone Ground Soldier	Vehicon Drone Ground Soldier

Espionage Team

Soundwave Intelligence Officer	Laserbeak	Ravage	Rumble	Frenzy

Buzzsaw	Ratbat	Reflector

Seekers

Air Commander Starscream	Skywarp	Thundercracker	Hotlink	Nacelle

Slipstream	Acid Storm	Ion Storm	Nova Storm	Sun Storm

Dirge	Ramjet	Thrust	Vehicon Drone Seeker	Vehicon Drone Seeker

Vehicon Drone Seeker

Constructicons

Bonecrusher	Hook	Long Haul	Mixmaster	Scavenger

Scrapper	Constructicons Gestalt Devastator

Stunticons

Motormaster	Breakdown	Dead End	Drag Strip	Wildrider

Stunticons Gestalt Menasor

Combaticons

Onslaught	Blast Off	Brawl	Swindle	Vortex

Bruticus

Decepticon Cybertron Forces

Overlord Cybertronian Commander	Shockwave Science Officer	Sixshot Six Clan Ninja	Straxus Polyhex Governor	Jhiaxus Ancient Scientist

Barrage	Chop Shop	Ransack	Venom

Decepticon Justice Division

Tarn	Helex	Tesarus	Vos	Kaon

Nickel

Seacons

Nautilator	Overbite	Seawing	Skalor	Snaptrap

Tentakil	Seacon Gestalt Piranacon

Terrorcons

Hun-Gurr	Blot	Cutthroat	Rippersnapper	Sinnertwin

Terrorcon Gestalt Abominus

Predacons

Arising from the ashes of the Great War, the Predacons are, at least in part, descendants of the Decepticons. Some sources suggest that they were born from what remained of the original five Predacons. By order of the Pax Cybertronia, they exist as something of an underclass, appearing to be equals, but firmly under the Maximals in the social order. This has led many Predacons to hold bitter grudges against the Maximals.
Predacons tend to take reptilian or arthropod beast modes, although this is not a hard-and-fast rule. They can also turn into less-than-realistic sea creatures and military vehicles.
The adjective for "of or pertaining to the Predacons" is Predaconial, though it is extremely common to simply substitute 'Predacon'.