"Every individual necessarily labours to render the annual revenue of the society as great as he can. He generally neither intends to promote the public interest, nor knows how much he is promoting it ... He intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for society that it was no part of his intention. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it. I have never known much good done by those who affected to trade for the public good."
Thus, the invisible hand is essentially a natural phenomenon that guides free markets and capitalism through competition for scarce resources.
BREAKING DOWN 'Invisible Hand'
Smith assumed that individuals try to maximize their own good (and become wealthier), and by doing so, through trade and entrepreneurship, society as a whole is better off. Furthermore, any government intervention in the economy isn't needed because the invisible hand is the best guide for the economy.