a month ago
A Forgotten Base is a strong encampment that generates Territory for the Forgotten faction. You can't move there, but destroying a Base earns you and your alliance the control over that territory. Attacking and destroying a Base is the only way forward to the center, but you will need an Army roughly around the same level as the Base.
A camp is a weaker forward base of the Forgotten and spawns always near player bases. They make for good raiding targets as their defenses are weaker than that of the other types of encampments.
Outposts are somewhere in the middle. They do not generate territory like Bases, but are stronger and provide more rewards than camps. They only appear near Tunnel Exits.
I hope that helps.