An active pickup is one that uses electronics to improve the sound and enhance its operation. There are a variety of ways to "Activate" a pickup. A simple "buffer" pre-amp will do the trick, but it will also amplify the hum and buzz the pickup produces. Just because a pickup is "active" doesn't guarantee you'll get great results. EMG pickups utilize an internal pre-amp (inside the pickup), which not only makes the pickup louder, it also reduces the noise!