Increasing equality, both within and between societies and countries - this is the goal of the 10th SDG. Even though human rights define every person as equal, this does not match the reality that many people in this world live in. From a financial point of view for example, 10% of the world's population owns 76% of the world's wealth. Inequality is not only a matter of finances and resources but also that of discrimination. 1 out of 5 people report to have made personal experience with discrimination. Especially in current times, social inequalities are a polarising issue, millions of people are displaced, the Black Lives Matter Movement has grown tremendously and people are still discriminated against based on their origin, age or other characteristics.
If you want to learn how to promote equality in the context of international cooperation, have a look at the UN's page on reduced inequality.