This chapter introduces the reader to some basic definitions and distinctions needed to form a context for greater understanding and application of the body of knowledge underlying this intriguing new construct that has emerged from research in the fields of neuropsychology and cognitive neuroscience. Executive functions are directive capacities that are responsible for a person’s ability to engage in purposeful, organized, strategic, self-regulated, goal-directed processing of perceptions, emotions, thoughts, and actions. The concept of independent but coordinated processes is important in understanding how executive functions direct and affect behavior. The extent to which executive functions can be considered as “synonymous” or “integrated” with the construct of intelligence depends upon the definition of intelligence that is being espoused. The distinction between the executive functions that direct cognitive processes and the cognitive processes directed by executive functions is critical for a clear understanding of the broader picture of a child’s cognitive strengths and weaknesses.