Sockets are the circular team-colored pads located around Fortresses and Outposts. Compatible units on sockets benefit from a slow health regeneration. Many stationary units require being placed into sockets to work. Some provide economical advantages, while others have a unique, special function.
Honeypots are functional even when not on a pad, but have severely reduced capabilities. Turrets and artillery also benefit from sockets through a doubled fire rate bonus, though are usually not considered as socket powered units.