Inequity is the virtually inevitable result of two powerful forces: prejudice on the level of the individual, and political imbalance on the social level. One can argue whether power imbalance and other social differences cause prejudice or the other way around. (In fact, while most of us are comforted by the notion of single variable answers to debates like this, the reality is more complex; each does enhance the other and which is the cause often reduces to a chicken and egg debate.) What is unarguable is that when prejudice produces discriminatory behavior and power imbalances reify individual behaviors into structural differences in access and treatment, gross social, political, and economic inequities result.
In common parlance, inequity and inequality may often be used interchangeably. Here, I presume a distinction: the term inequality being descriptive and the term inequity being normative. Inequality refers to a distribution of some good within in which some obtain more than others. Inequity goes beyond this: the distribution is not only unequal; it is unfair and unjust.