Biotics manipulate mass effect fields using dozens of element zero nodules within their nervous system that react to electric stimuli from the brain. Amplifiers allow biotics to synchronize the nodules so they can form fields large and strong enough for practical use. Amplifiers can improve a specific discipline or talent.
An implant is surgically-embedded interface port into which amps are "plugged in". On humans, the implant is usually placed at the base of the skull for convenient access, though the user must be careful to keep it free of contaminants.
Implant ports can fit a variety of amps, and there is a growing market for modifications and add-ons. The finest quality implants and amps are manufactured by asari artisans, but the Alliance's L3 implants - first deployed in 2170 - are a significant step forward.