Yagi Antennas are highly directional antennas. They consist of multiple elements (pieces of wire/metal) all situated perpendicular to the direction of the signal they are attempting to recieve. Yagi antennas typically consist of an odd number of elements with the middle element being the only driven element. The other elements are totally passive. The driven element is tuned for the frequency of interest while the non-driven elements are either longer or shorter then the frequency that is trying to be tuned. The longer elements act as reflectors and reflect electromagnetic energy back toward the active element while the shorter elements constructively interfere to amplify the signal toward the receiving element. Thus to get the best reception, one points the shorter elements toward the transmitting tower and the longer elements away.