A Cyber Planet Key (Planet Force in Galaxy Force) is one of four mystical items that form the crux of Transformers: Cybertron's plot; in order to stop the black hole that is threatening the universe, the Autobots must gather all four. Also seeking to attain them are the Decepticons, who want to use their power for their own ends.
The Cyber Planet Keys are formed from the spark of Primus, and were used eons ago in the Space Bridge project that was meant to link all populated planets together. They were carried to various planets by four Cybertronian spacecraft, the Atlantis, the Ogygia, the Hyperborea and the Lemuria. They were intended to transform the worlds into mirror images of Cybertron. All four are controlled by a device called the Omega Lock, and when they are all inserted, they awaken Primus's power. They have also exhibited other properties, which include influencing their surroundings and sending out strange signals.
Unfortunately, the effort failed, and the four Cyber Planet Keys were lost. They would remain that way for eons, until the black hole threatened Cybertron. At that point, Vector Prime emerged, and told the story of the Keys to the Autobots. Eventually, they agreed to attempt Vector Prime's plan, but unfortunately, Megatron also learned of the scheme and began his own effort to gain the Planet Keys, with the intention of using them to increase his own power.
The Cyber Planet Keys were fashioned into four keys, each marked with a symbol and colored gold. As they are formed from Primus's spark, they have been known to respond to strong emotions exhibited by Cybertronians, as if a god were responding to the wishes of his people. In addition to their power manifesting as the weaker Cyber Keys, they have done such fantastic things as reformat Transformers who have suffered heavy damage, such as they did with Overhaul/Leobreaker, Hot Shot, Red Alert, and Scattorshot and change their Cyber Key identity. They seem to work in accordance with the will of Primus, doing such things as granting Leobreaker and Wing Saber the ability to combine with Optimus Prime, but the Decepticons have been known to access their power as well (most likely by merit of being Transformers with sparks themselves).
The four Cyber Planet Keys were found on Earth, Velocitron, Jungle Planet and Gigantion. On Velocitron, the Key was disguised as a racing trophy, and on Jungle Planet, it was disguised as a dragon statue. The Earth Key was possessed and hidden by Evac in ice, and the Giant Planet Key lay at the very center of planet in the spaceship Lemuria. Finally, the Autobots found the Cyber Planet Keys and the Omega Lock, and awoke Primus, who shut down the black hole, saving Cybertron and the universe. The four planets started a new space bridge project, and, finally, peace arrived.
Cyber Keys (Force Chips) are objects that are similar in nature to the Cyber Planet Keys. Described by Vector Prime as "Tiny fragments of the power of Primus", they are best described as a quick power up that energizes a Transformer and bestows them with added power. This process is similar to powerlinking with Mini-Cons in Transformers: Armada, which resulted in a rapid "evolution" that unlocked a hidden ability.
The technology for using a Cyber Key exists in all Transformers. Knowledge of it was lost by the Transformers on Cybertron until it was revealed to them by Vector Prime. On Earth, Speed Planet, Jungle Planet and Giant Planet, however, the knowledge was retained. When summoning one, a Transformer cries out "CYBER KEY POWER!" (FORCE CHIP, IGNITION! in Galaxy Force), creating a "warp" that causes the Cyber Key to shoot down from the sky and fly into its access slot. The new ability is then activated, which usually manifests as a hidden or empowered weapon. They are usually called willingly, but in the case of Optimus, Jetfire, Hot Shot, and Landmine, they came to their users of their own accord in times of extreme emotion.
There are multiple varieties of Cyber Keys, four of which mirror their Planet Key counterparts. The other varieties do not have Planet Key versions, and may manifest in those forms due to the specific energies of their wielders. One theory states that the type of Cyber Key called upon by a Transformer depends on which planet the individual is most in tune with. Several characters, most notably Jetfire and Overhaul, have toys that are packaged (in the US version) with different keys than what they use in the show.
Due to their great similarity to the Cyber Planet Keys, it can be assumed that the Cyber Keys are simply smaller, less powerful versions of the Planet Keys.
Also in the episode "unfinished" it appears all the planet leaders can can access a golden aura mode where their strength is increased enough to push the rockets back into place. Optimus Prime can enter this golden mode however this is done using the power of the Matrix of Leadership.