Memory refers to the processes of encoding, storing, and retrieving information over time. There are three main stages of memory: sensory memory, short-term memory, and long-term memory. Information is encoded through automatic and effortful processing and can be stored through different memory systems like procedural, episodic, and semantic memory in long-term storage. Memories are retrieved through recognition and recall. Forgetting can occur due to encoding failure, memory decay, interference, or retrieval failure. Spaced practice over time leads to better long-term recall compared to massed practice or cramming.