This is the Forgotten Construction Yard. Destroy it to destroy the whole base, wiping it off the map and claiming all the resources contained within.
This is the Forgotten Harvester. It is always on either Tiberium or Crystals. Destroy this to gain resources gathered in the form of crystals or Tiberium.
The Silo will hold precious Tiberium and Crystal resources. Destroy it to claim whatever resources the Silo holds.
The Refinery will contain cash, Tiberium, and Crystals, all for the taking. Destroy it, and claim them all!
The presence of a defense HQ usually means a Forgotten base is stronger than a basic camp. Destroy this to claim some resources, in the form of Tiberium or Crystals.
This is the monetary exchange of the Forgotten. Destroy it for a quick cash bonus, which can be used in conjunction with research to buy new units!
This is the building that creates Forgotten vehicles. Destroy it for Tiberium and Crystal resources.