The Borg manifest as cybernetically-enhanced humanoid drones of multiple species, organized as an interconnected collective, the decisions of which are made by a hive mind, linked by subspace radio. The Borg inhabit a vast region of space in the Delta Quadrant of the galaxy, possessing thousands of vessels.
They operate toward the fulfillment of one purpose: to "add the biological and technological distinctiveness of other species to [their] own... [in pursuit of] perfection". The concept of perfection is the unifying idea at the core of the Borg. The pursuit of an unemotional, mechanical perfection is the Borg's only motivation.
This is achieved through forced assimilation, a process which takes individuals and technology, enhancing and controlling them. Originally presented as an autonomous collective, the ideas of a Borg Queen and central control were introduced in First Contact.