In a nutshell, Cognitive Load is the amount of “Brain Power” required to understand something. This could be perception, problem solving or juggling things in memory.
The term cognitive load is used in cognitive psychology to illustrate the load related to the executive control of working memory. Theories contend that during complex learning activities the amount of information and interactions that must be processed simultaneously can either under-load, or overload the finite amount of working memory one possesses. All elements must be processed before meaningful learning can continue.