Creators, like artists and photographers spend their lives studying, preparing, writing, mixing, creating for their fields of work. They want credit and to be paid for the fruits of their labor. So, when you want to take a creator's work, you should ask permission first. Respecting copyright is the polite thing to do.
It attempts to balance owner's rights against user rights by enabling the owners to bear the fruit of their labor and guaranteeing the public's right to reasonable and fair access.
Here's the nitty gritty on copyright in fact format.
Watch The VlogBrothers, Hank Green explaining The Bizarre State of Copyright [3m 56s] in reply to, author John Green sharing Across Three Continents: A Tale of Tumblr, Copyright, and Excellent Posters
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