MATLAB (matrix laboratory) is a numerical computing environment developed by MathWorks. It supports matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages.
MATLAB is widely used as a platform to design experiments and analyze data for the cognitive sciences.
This tag can be used for questions on MATLAB, but posts need to have their basis in the Cognitive Sciences. For example, if you have a question on the Psychophysics Toolbox this site will most likely warmly welcome your questions. However, general MATLAB programming questions, baring no relation to the Cognitive Sciences, or are only slightly related should be asked elsewhere on the Stack Exchange network, such as StackOverflow.SE, or SuperUser.SE. For more tips on where to post your MATLAB questions when unrelated to Cognitive Sciences see this meta post).
Source: Wikipedia page on MATLAB