Mass Effect & Mass Effect 2
Biotics manipulate mass effect fields using dozens of element zero nodules within their nervous systems that react to electrical stimuli from the brain. Amplifiers allow biotics to synchronise the nodules so they can form fields large and strong enough for practical use. Amplifiers can improve a specific talent or discipline.
An implant is a 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 clear of contaminants.
Implant ports can fit a wide 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.