“Action research aims to contribute both to the practical concerns of people in an immediate problematic situation and to further the goals of social science simultaneously. Thus, there is a dual commitment in action research to study a system and concurrently to collaborate with members of the system in changing it in what is together regarded as a desirable direction. Accomplishing this twin goal requires the active collaboration of researcher and client, and thus it stresses the importance of co-learning as a primary aspect of the research process”

(Thomas et. al., 1986) reference

Put simply, action research is "learning by doing" - a group of people identifies a problem, do something to resolve it, see how successful their efforts were, and, if not satisfied, try again.

Gerald Susman gives a somewhat more elaborate listing. He distinguishes five phases to be conducted within each research cycle. While there are over 5 different paths one could take, the one by Gerald Susman is the most popularly used.