Beamforming is the combination of radio signals from a set of small non-directional antennas to simulate a large directional antenna. The simulated antenna can be pointed electronically, although the antenna does not physically move. In communications, beamforming is used to point an antenna at the signal source to reduce interference and improve communication quality. In direction finding applications, beamforming can be used to steer an antenna to determine the direction of the signal source. This introduction to beamforming covers the basic properties of antennas and antenna arrays, then explains how beamformers are built using digital radio hardware and DSPs. Super-resolution direction finding is also explained.