Episodic memory is a form of memory which allows someone to recall events of personal importance. Together with semantic memory, it makes up the declarative section of the long term memory, the part of memory concerned with facts and information, sort of like an encyclopedia in the brain. The other type of long term memory is procedural memory, which is the how-to section of the brain.
The primary contrast between episodic and semantic memory is that episodic memories are memories which can be explicitly described and stated, while semantic memory is concerned with concepts and ideas. For example, the concept of a table is housed in the semantic memory, but when someone describes his or her kitchen table, this is an episodic memory. Procedural memory can also interact with declarative memory, as for example when someone drives a car, using procedural memory to remember how to drive, semantic memory to define a car, and episodic memory to recall specific driving experiences.
Episodic memories can pertain to general or specific events, such as what it feels like to ride a train, or a specific event which occurred on a train. It can also include facts, such as the names of world leaders, and so-called “flashbulb” memories, which are formed during periods of intense emotion. A classic example of a flashbulb memory from the 20th century is the assassination of President Kennedy, an event which was vividly remembered by people who were alive at the time.
It only takes one exposure to form an episodic memory, which is probably something which evolved early in human evolution, to teach people to avoid making potentially deadly mistakes. For example, someone who almost drowns as a child will often develop a fear of water in response to this single experience. People engage in episodic learning every day, but children often provide very striking examples of episodic learning, since they are exploring a world which is primarily unfamiliar to them, and hence they constantly have new experiences which are filed away in the episodic memory.
This area of the long term memory is a critical part of identity. People are shaped by the events they participate in and interact with, and loss of episodic memories can cause people to experience confusion or distress, as they lack a context for their identities. Some researchers have suggested that episodic memory sometimes turns into semantic memory over time, with the brain lumping a family of similar experiences together to create a semantic concept. For example, distinct memories of various burns may be bundled together into the semantic memory to provide a concept of “hot,” along with information about which kinds of things tend to be hot.