Over the years, many multiple memory systems have been proposed. The most widely accepted today are nondeclarative/declarative memory, semantic/episodic memory, and implicit/explicit memory.Declarative memory stores facts and can be consciously discussed.
Semantic memory is memory of meanings and concept based understanding
Episotic memory is the memory of events, times and places
Explicit memory is exact memories like "what you had for breakfast"
Implicit memory is "memory that can't be verbalized but that can affect performance on some task without conscious awareness. For example, sometimes you can recognize a multiple choice answer without ever realizing you learned the information in the first place. Eich, Macaulay, Loewenstein, and Dihle (1997)
Don't forget, there are also "false memories" that can be mistaken for real memory and the person honestly thinks they really have been through things that never happened.
More info at Brainconnection.com -- One of the interesting ideas is that infants do not have the ability to process language so they can have no connections to make memories.
It suggests that emotional memories may be easier to recall but they are speaking about 1 and 5 year olds.