(Hebrew darash, to seek, study, or inquire)
The investigation and explanation of scripture.
By claiming to fill in gaps in the biblical narrative, it allows the interpretter to derive the meaning he or she is seeking. Thus It is an effective technique for adapting the Torah to new environments and behaviours.
An example of this technique is to treat an uncomfortable biblical stricture as being allegorical or metaphorical, and not actually meaning what it literally says.