John Rawls argues that inequality of result is acceptable in a society so long as there is true equality of opportunity. He argues that it is acceptable to give (for example) higher pay and higher status to people in a given profession if all people have an equal opportunity to enter that profession.
Rawls understands that not all people have the same abilities and talents. He takes this into account in his formulation of what equality of opportunity means. What Rawls says is that all people who have the same talents and the same amount of ambition and willingness to work must have the same opportunities. A person who is not very smart does not have to be admitted to an Ivy League school. Neither does a brilliant but lazy person. But two people who are equally talented and equally motivated must have the same educational and economic opportunities, regardless of whether they are born rich or poor.
The important aspect of Rawls' formulation, then, is that he requires equal chances for people who are similar to one another in talents and ambitions.