The document discusses the nature of memory and describes it as retaining and recalling information over time depending on the cognitive task. It outlines the three stages of memory as encoding, storage, and retrieval. Encoding is the initial processing and registration of information, storage is the retention of information over time, and retrieval is bringing the stored information back into awareness to be used for tasks like problem-solving. The document also likens human memory to a computer with RAM for temporary storage and a hard disk for permanent storage, and notes a stage model of memory proposed by Atkinson and Shiffrin.