From GameWatcher: “Anthem is the latest game from BioWare, and unlike their previous games, it’s an online-only loot shooter like Destiny. One of the best parts of Destiny is the awesome Raids, which are more of a challenge and offer better loot. You’ll find this game has its own version of Raids called Anthem Strongholds.”
Source: N4G PC Anthem Strongholds – How to Unlock Strongholds in Anthem