Insider
An insider is a member of any group of people of limited number and generally restricted access. The term is used in the context of secret, privileged, hidden or otherwise esoteric information or knowledge: an insider is a "member of the gang" hence knows things outsiders don't, including insider jargon.
In our complicated and information-rich world, the concept of insider knowledge is popular and pervasive, as a source of direct and useful guidance. In a given situation, an insider is contrasted with an outside expert: the expert can provide an in-depth theoretical analysis that should lead to a practical opinion, while an insider has firsthand, material knowledge. Insider information may be thought of as more accurate and valuable than expert opinion.
Roles
There are many popular cultural roles ascribed to the insider.
In criminal and social justice, whistle-blowing and leaks are seen as (often heroic) efforts of individual insiders to right wrongs by making secret information public, usually in David and Goliath situations (e.g. by revealing transgressions of governments, large corporations or other powerful organizations). When whistle-blowers are cultivated by outside forces, they are known as informants and informers.
