There are three main types of memory: sensory memory, which briefly stores perceptual information; short-term memory, which retains information for around 20 seconds; and long-term memory, which can store information for years. Information is encoded from sensory memory into short-term memory and then must be rehearsed to be consolidated into long-term memory. There are three main types of long-term memory: semantic, episodic, and implicit. Memory is influenced by encoding, storage, and retrieval processes and can be impaired by conditions like amnesia.