Accelerated Production

When you have multiple copies of a structure that can produce units, each building participates in the training process. Each additional building you create boosts the production speed of units that structure can produce.

For example, if you have two Training Facilities, all infantry that you produce from one facility will build twice as fast because the second one is aiding in the production process. Add additional Training Facilities and that rate increases further.

On the other hand, each building can also produce units on its own. If you select a specific structure and click on an icon in the Build Menu, that unit will be constructed specifically at that facility. Any facilities which are not presently training units will participate in speeding the production at other facilities. But you can select each facility in turn and give them different units to train. If you do this for all of your buildings, the production of each unit will no longer be accelerated; however, you are now training multiple units simultaneously.

Thus, you have a choice: you can build each unit quickly but have them produced one at a time, or you can train multiple units at once but at a slower speed.

When you do not have a structure selected and you choose to train a unit, the unit is trained automatically at your primary facility of the appropriate type.