Transformers is the well-known franchise that follows the interstellar war between the noble Autobots and ruthless Decepticons, two factions of sentient humanoid machines locked in an eons-old civil war that began on their homeworld of Cybertron and brought them to Earth, catching Humanity in the crossfire. These machines have the amazing capability to assume other forms, generally Earth vehicles, to remain on the planet incognito as robots in disguise - which earns them their name as Transformers. This particular theme is based around the continuity established by the Michael Bay Transformers films that began in 2007 with Transformers and was then followed by the three sequels - Revenge of the Fallen, Dark of the Moon and Age of Extinction.
As mentioned, this iteration covers the war between the Autobots (led by Optimus Prime) and Decepticons (led by Megatron). This timeline primarily concerns itself with the battles on Earth during and after Megatron's quest for the AllSpark the all-powerful source of creation that was responsible for all life on Cybertron. While Megatron failed in his quest and was, indeed, killed (temporarily) by Sam Witwicky, the war did not end there. Therefore, this timeline also follows the destruction of the Fallen - an incredibly ancient and incredibly powerful foe of the Autobots - in Egypt as well as the betrayal of Sentinel Prime, the former leader of the Autobots, and the subsequent destruction of the teleportation gate known as the Pillars. Even Cybertron is utterly destroyed in this timeline, leaving the Autobots to claim Earth as their new home. In the aftermath of their defeat, the Decepticons may be scattered and broken but, as always, the war is not over. Perhaps it will never be over. And perhaps there are forces that are weary of the Autobots remaining on Earth, wishing to rid the Earth of all Transformers, and perhaps there are greater forces in the cosmos who are putting their pieces in place for one final endgame...
Ancillary materials such as novels and comics are also acceptable but the world as demonstrated in the four films is considered 'primary canon'.
A few minor points of interest that differentiate this canon from previous Transformers timelines include: a somewhat more realistic or 'grey' take on the Transformers mythos, including conservation of mass between vehicle and humanoid forms. It also includes Autobots who are used to working with the human military and a bit more used to war. Temperature extremes are deadly to Cybertronian life in this timeline and the general treatment of the world leans towards 'shades of grey', including when it comes to the characterisation of the Autobots.