FangTheCat Look it up on wikipedia, this is what I found there (way too much to write xD) Here is what wikipedia says:
Stellaris is a real-time grand strategy game set in space, beginning in the year 2200. Players take control of a species in its early stages of interstellar space exploration, right after the invention of faster-than-light (FTL) spaceship technology, ready to claim a place as one of "the species of the stars". Depending on several factors, such as the ethics of the civilization and the player's desires, the ultimate goal of the empire can range from galactic conquest, hoarding of resources and technological supremacy, to the peaceful coexistence or absolute destruction of all sentient life. The player controls ships, including science, construction and military vessels. Combat includes space combat and ground combat and is more centered towards the bigger picture, preparation, and strategy. There are also diplomatic options such as alliances and trade agreements with other races.
And yes, each faction is VERY costumizable, I just had to remove the middle paragraph for safety reasons.
The player begins with a single planet in their territory, several mining and/or research stations, a construction ship, a science ship, three small warships, and a spaceport. Early gameplay consists of exploring and colonizing space, while mid-game activities focus on diplomacy and governing an empire. In the late game, crisis events can occur that have galaxy-wide implications—for example, an awakening of dormant sentient AI or an invasion by extra-dimensional or extra-galactic forces, the former two always being triggered by careless empires. Paradox hoped that this would address a common late-game problem in 4X style games; whereby one faction is so powerful that their eventual victory is inevitable, resulting in frustrating gameplay.
Here is where you can find where I found all of this:
https://en.wikipedia.org/wiki/Stellaris_(video_game)