How does money become "black money"?

"Black money" -- a term that blows up every budget season, a color that you cannot see, but still somehow is allowed to be "whitened".

So, what is this mysterious "black money"? Can anyone have it? Why can one get away with it?

As the first installment of a series of content on this year's budget, The Daily Star starts with a new show "Star Unfolds", where complex issues are dissected and presented in a simplified manner for the audience. Today, it is time to unfold "black money".