Summary Array processing technique represents a breakthrough in signal processing. Many applications and problems which are solvable using array processing techniques are introduced. In addition to these applications within the next few years the number of applications that include a form of array signal processing will increase. It is highly expected that the importance of array processing will grow as the automation becomes more common in industrial environment and applications, further advances in digital signal processing and digital signal processing systems will also support the high computation requirements demanded by some of the estimation techniques. In this article we emphasized the importance of array processing by listing the most important applications that include a form of array processing techniques. We briefly describe the different classifications of array processing, spectral and parametric based approaches. Some of the most important algorithms are covered, the advantage(s) and the disadvantage(s) of these algorithms also explained and discussed. See also Phased array Space-time adaptive processing Periodogram Matched filter Welch's method Bartlett's method SAMV References Sources S. Haykin and K.J.R. Liu (Editors), "Handbook on Array Processing and Sensor Networks", Adaptive and Learning Systems for Signal Processing, Communications, and Control Series, 2010. E. Tuncer and B. Friedlander (Editors), "Classical and Modern Direction-of-Arrival Estimation", Academic Press, 2010. A.B. Gershman, array processing courseware Prof. J.W.R. Griffiths, Adaptive array processing, IEEPROC, Vol. 130,1983. N. Petrochilos, G. Galati, E. Piracci, Array processing of SSR signals in the multilateration context, a decade survey. Sensors Multidimensional signal processing