The document discusses Information Processing Theory (IPT), which describes how knowledge enters and is stored in memory in three stages: encoding, storage, and retrieval. It explains the different types of knowledge and the stages of IPT - sensory register, short-term memory, long-term memory - and the processes of attention, rehearsal, and organization that guide information flow. Forgetting can occur due to decay or interference, but strategies like elaboration and context can aid retrieval.