Equity and justice are closely related. While not absolutely identical, they belong to the same genus and are both morally good. What is equitable is just, in one sense, but in another sense it is higher than what is just since equity is the principle applied to correct justice when it errs.
Laws are expressed in generalized, universal terms, but there are always particular cases which do not fit into this abstract framework. Such generalizing, which is based on the majority of cases, is necessary if the law is to be functional, but there are occasional errors or oversights. When a particular case falls outside the scope of the law's generalized formulae, the shortcomings or omissions in the law are rectified by the principle of equity in accordance with what appears to have been the general intent of the law or legislator. In fact, by applying the principles of equity in this way, one tries to do what the legislator himself would do were he present and familiar with the particular case.
Equity is correction of the law according to the principles of universal justice in situations for which the law is too abstract or generalized. An equitable man is not a stickler for the letter of law; he will be satisfied with less than his legal share in certain situations if he feels this is more just.