The command computer requires a central location from which to operate.
The Central Processor provides this location and houses the bulk of the main command computer.
The Central Processor is the first building you will have as a new player.
It provides the center hub for your first base.
The Central Processor can build Constructors and with higher levels of Expansion Technology it can produce a Colony Ship which can be used to found another base.
You will want to protect your Central Processor, if it is deactivated an enemy can move a transport close to it and steal resources from your base.
The Central Processor can be enhanced to provide 60% theft security.