Declarative memory is the aspect of human memory that stores facts. It is so called because it refers to memories that can be consciously discussed, or declared. It applies to standard textbook learning and knowledge, as well as memories that can be 'travelled back to' in one's 'mind's eye'. It is contrasted with procedural memory, which applies to skills. Declarative memory is subject to forgetting, but frequently-accessed memories can last indefinitely. Declarative memories are best established by using active recall combined with mnemonic techniques and spaced repetition.
Types of declarative memory
There are two types of declarative memory:
- Semantic memory
- Factual knowledge independent of time and place
- Episodic memory
- Theoretical knowledge of a specific moment in time and place
Some people believe that episodic memory and semantic memory are really just one type of memory. However, most believe they are quite different, and indeed distinct. 
Physically speaking, declarative memory requires the medial temporal lobe, especially the hippocampus and related areas of the cerebral cortex. The famous amnesiac H.M. had a great of his medial temporal lobe removed and had a primarily declarative impairment (specifically, his episodic memory).
- Tulving, E., & Schacter, D.L. (1990). Priming and human memory systems. Science. 1990 Jan 19;247(4940):301-6.
- Tulving, E. (1984). Precis of Elements of Episodic Memory. Behavioural and Brain Sciences, 7, 223 – 268.