UFO: Extraterrestrials GOLD is a new GOLD edition which includes a number of changes and improvements giving a player a new look on the classic game: new maps, possibility to hire soldiers, globe UFO swarms and configurability.
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.