It means what the words themselves mean. Conservatives have been brainwashed to think it means something other than what it really means.
I guess I always thought of it like even though everyone is not born with the same abilities nor raised in the same environments, each individual can take personal responsibility and access the knowledge and other opportunities that are publicly available to everyone.
But now I see that my interpretation is not the only one.
Liberals want to make things equal for everyone by lowering standards. Then they wonder why we are falling behind other nations.