Memory involves the complex systems by which a person perceives, remembers and recalls information and experiences. Memory is not a single process but consists of inter-related subsystems. The stages of memory include attention, encoding, storage, and retrieval. "Encoding" is the process of registering information, "storage" refers to maintaining it in memory and "retrieval" is the act of recalling it again. These stages are closely linked and interact with one another. Different brain areas have been identified that are involved in different stages of memory.

There are various types of memory. One clinically important distinction is between two forms of time-dependent memory: long-term versus short-term memory. This distinction is primarily based on the duration of memory store and the capacity of the store. Long-term memory can be further divided by the type of information that is processed. Two broad categories that are processed differently are called declarative and nondeclarative memory. The distinction between episodic and semantic memory is particularly important in cognitive rehabilitation. Memory loss can also be specific to the verbal or nonverbal material. This distinction implies that memory for verbally based information is encoded and stored separately from information that is not easily verbally labeled. Individuals with focal injuries are more likely to have material-specific memory impairment than are individuals with diffuse involvement.

Various systems and structures in the brain influence different aspects of memory. However, it is the functional effects of memory impairment that ultimately guides the direction of rehabilitation. In Cognituner memory has been divided into time-dependent memory (short-term vs. long-term memory) as well as to modality-specific memory (verbal vs. non-verbal memory).