X-COM: Earth's top-secret eXtraterrestrial COMbat unit The Place: America - early 21st century The Mission: Eradicate the extraterrestrials Alien forces have invaded Earth and are terrorizing the population.
Most popular community and official game content for the past week.  (?)
What does popular mean?
It means the content you're seeing has been rated up more than it has been rated down for the given time period.