Social manufacturing refers to all non-ship manufacturing performed at colonies.
Social manufacturing is allocated by assigning population to manufacturing, and then setting the social/military manufacturing slider. The total multiplier to social manufacturing is independent of the multiplier to all manufacturing: a +20% bonus to manufacturing and a +20% bonus to social manufacturing will result in a 1.44x multiplier to net social manufacturing.
The primary type of social manufacturing is improvements: constructions that take up one hex each on the planet surface and provide a bonus to the colony.
Social manufacturing may be spent on projects to increase the output of other resources. Each 10 points of social manufacturing gives +10% to the production of the resource specified by the project for that turn:
The more production a planet has, the more efficient these projects are; however, they are generally less effective than appropriately specialized planets unless extreme amounts (~hundreds) of production are reached.
Synthetic races increase their population via project.
Colonies may produce shipyards in order to manufacture ships. The shipyard itself is social manufacturing; however, the ships are military manufacturing.
Military manufacturing refers to the part of overall production that is used to manufacture ships of all classes at shipyards.
Military manufacturing is allocated by assigning parts of your economy to manufacturing, and then setting the social/military manufacturing slider. Unlike social manufacturing, modifiers that affect only military manufacturing are extremely rare. This means that most important ways of enhancing military manufacturing are those that increase your overall manufacturing.
One difference between Military and Social production is the fact that up to five planets are able to combine their military output at a single shipyard.
Only limit to this is the diminishing returns on long distances between the planets, or sponsors, and the shipyard. The link is at full capacity when the distance between the shipyard and sponsor is six tiles or less, and the percentage of the original military production that is available to the shipyards starts to drop as the distance increases after that.
Certain race traits and ideologies can decrease the effects of distance on the production.