Kinmoku is where Fighter, Maker and Healer are really from. Their planet was destoried by Galaxia which led them to Earth. In the anime, not much is mentioned the Lights never adress their home as Kinmoku they always say "our home planet" or something along the lines of that.
In the manga, Kakyuu is princess of the Tankei Kingdom on Kinmoku. It's not said whether know like the the Silver Mellinum or Moon Kingdom. In the anime it never mentioned if Kakyuu was the princess of just this kingdom or the entire planet similar to Neo Queen Serenity or Princess Serenity or the inners/outers being princesses of their entire planets.
In episode 194, a small vision through Seiya's song to Kakyuu is shown before the battle. Surrounding the planet is three colors the same as the colors of the Starlights when they turn into shooting stars. Red=Seiya Green=Yaten and Blue=Taiki...it's unknown what they truly are. Kakyuu states that soliders are born from stars and planets like Jupiter, Mars, Uranus etc. So, around the planet it could be their home stars or their own planet of their dreams or something or a place for privacy.
It is known however, the three lights were the only ones to survive the battle with Galaxia. Healer says in 196 when Galaxia's battle starts she says "This is just what happened on our planet!" This is happening when Galaxia is talking on a tv jumbo screen. I think personally maybe that on Kinmoku before the battle Galaxia nested on Kimoku and sent animates out just like on Earth and when the final battle came annocued it just like on Earth.
The planet revoles around blossomes, olive blossomes. This is obvious in 194 in Seiya's vision of the planet you see blossomes in the background floating around along when the Starlights transform blossoms show up on the sides, left and right and Fighter, Healer or Maker in the middle. Plus, Kakyuu has the same symbol of a olive blossom on her forehead. She also is adressed by Galaxia as "Princess Of Fragrant Olives." Before her star seed is taken.
Kimokusei translates in English to Planet Kinmoku or Kimoku Star...this reffers to Orange Osmanthus olive trees.
In the anime, the Starlights say goodbye to the inners and leave because Kakyuu said "the other will be waiting for us." Yaten says they'll create a new world with their princess. In the manga however, after they die, yes they die in the manga they don't have a farewell like on the roof top. It's stated that all the star seeds go back to their rightful owners so what probably happened is the lights arrived by on Kinmoku but at the end Usagi and Mamoru get married. Nothing is said of the Starlights.
