The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is the first high energy physics experiment to use LAPPDs. The experiment uses Gd-loaded water to study for neutrino interactions and produce a measurement of the neutron yield out of neutrino-nucleus interactions. LAPPDs allow us to better localize the interaction point of the neutrinos. But what exactly are LAPPDs, besides a challenge to say it three times fast? As their name implies, these Large Area Picosecond Photo-Detectors are a novel type of light sensor with a large sensitive area and enhanced time resolution. In this talk I will explain how LAPPDs work and how they enhance the physics of ANNIE.