These are achievements added with DLC that are unique. Most come from the Wonders of The Ancient World DLC. They can be unlocked in a scenario or a normal game. Some can only be unlocked by a certain civilization.
“Enter a snow tile with the Norwegian ski infantry (Denmark unique unit) Denmark - The Vikings DLCWhere's the Biathlon?
“Build Statue of Zeus and Temple of Artemis in the same city. Wonders of The Ancient World DLCBolt and Arrow