In physics and optics, transparency refers to the property of a substance to transmit light (or some other form of energy). Since information encoding requires energy, one could say that transparency refers to the capacity of a "channel" to transmit information. These physical and technical uses of the term can be applied symbolically to human and institutional behaviors. We say, for example, that a man's behavior is "transparent" if we feel he is guileless - honest, that he has nothing to hide, that he is "telling it like it is", that "what you see is what you get"..
Transparency, in this metaphorical sense, is essential, we believe, to the functionning of any democracy worthy of the name. Information must flow freely from lower levels of social / command hierarchies to the top, and from the top to the bottom. Exceptions, of course, have always been allowed for "State Secrets", especially in times of war: one does not want one's invasion plans to fall into the hands of the enemy; we want to catch him off balance. This is why it has been remarked that "truth is the first casualty of war".
But why, exactly, is transparency so important to the functionning of democracies? If one takes the term literally, democracy means rule by the common people:
Taken at face value, the answer is simple! Rulers, in order to rule competently, require information. For the people to rule competently, it, too, requires "unbiased", "objective" information. "Transparent" channels of information provide the required objectivity and lack of bias: they do not distort, alter or color the information that flows through them.
It should be obvious - I hope - that terms such as "objectivity" and "unbiased" are to be taken in the sense of goals or objectives which we should aim for and that different people, with different perspectives and agendas, will legitimately argue over whether or not a given piece of information is indeed "objective". Such divergences do not render the goal of transparency impossible; they merely stress the need for an open consensus on what terms like "objectivity" and "bias" mean in a given socio-historic context. Transparency is a difficult, subtle, self-referential ("recursive") term, included in its own definition (the "chicken or egg" conundrum). Defining - and implementing! - transparency would appear to require a minimum of goodwill and respect for honest opposition - the existence of a vital "civil society" open to debate and the expression of various opinions and views.
With the spread of modern means of communication and mind control and the consequences of untoward consequences of action by major players (nuclear reactor manufacturers, governments..), transparency is now, at the dawn of the 21st century, more important than ever. Various groups are now coalescing, focusing on the various ways to implement or safeguard governmental transparency: