Infrared detection systems usually need close-packed detectors in order to increase their spatial resolution.The crosstalk between individual elements in a focal plane array (FPA) occurs when the infrared photons incident on a particular detector's active area in the array generate signals in another detector. The resolution performance of a FPA may be limited by the crosstalk. The dominant form of the crosstalk occurring in a high performance photovoltaic array is associated with the photogenerated carriers diffusing laterally between adjacent elements within the FPA. Starting from basic concepts, the research progress and the understanding and comprehension of crosstalk are presented.