"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
these are life, liberty, and the pursuit of happiness."
It means that everyone has equal rights, and in this case the excerpt is referring to natural rights - rights everyone has as soon as they are born. (Natural rights was an idea created by Enlightenment thinker John Locke)
