Memory plays an important role in learning and development. There are three main types of memory: sensory memory, short-term memory, and long-term memory. Sensory memory only lasts 1 second, short-term memory lasts 20-30 seconds through chunking information, and long-term memory can store information indefinitely. Memory involves encoding, storing, and retrieving information. It is influenced by both intrinsic factors like age and extrinsic factors like environment. There are several theories that attempt to explain memory and forgetting, including memory trace theory, levels of processing theory, and interference theory.