Counterbalancing is a term describing any technique used to vary systematically the order of conditions in an experiment to distribute the effects of time of testing, for example; practice and fatigue, so they are not confounded with conditions.
It is a method of controlling for order effects by giving half of a sample Test A first, followed by Test B, and giving the other half of the sample Test B first, followed by Test A. Moreover, on a within-subjects design, Counterbalancing is a procedure to minimize threats from order effects and time-related factors by changing the order in which treatment conditions are administered from one participant to another so that the treatment conditions are matched with respect to time. The goal is to use every possible order of treatments with an equal number of individuals participating in each sequence.