What did the declaration of independence do?

The Declaration of Independence formally declared the American colonies' intention to separate themselves from British rule.

The Declaration of Independence starts with a title, asserting it as the unanimous assertion of all 13 colonies, declaring their independence as the United States of America.  This is the way it is titled:

Then, the opening paragraph of the Declaration says, "When in the Course of human events it becomes necessary for one people to dissolve the political bands which have connected them with another and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation. "

Following that are the lines from the document that are probably the most famous:  "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness."

The Declaration asserted the legitimacy of the new United States of America in establishing itself.  The document laid out numerous "facts to be submitted to a candid world" -- points that demonstrated that the British king had been seeking to establish "an absolute Tyranny over these States" (the colonial states which were declaring their independence).  

powers  are  denied  to the  national governmentin three distinct ways: some  powers, such as the  power  to levy duties on exports or prohibit the freedom of religion, speech, press, or assembly, are expressly  denied  to the  national government  in the  constitution.

a) the colonists began to see themselves as different from people in britain.