Pastor John MacArthur provides a helpful summary of this key concept using three words: Law, Grace, and Obedience.
1) Righteousness is defined by Law.
You want to know what righteousness is? What it is to be right with God? Holiness is defined by the Law. The holy Law of God defines perfect righteousness (see Rom. 7). Our Creator's holy character is revealed in the righteous Word of truth (see Psalm 119). As we gaze into God's righteous Law it reveals our many blemishes and moral imperfections (like a mirror).
We need to be opposed to the light of God's word to not affirm that "there is none righteous, no not one" (Romans 3) and that we "ALL fall short of the glory of God" (Rom. 3:23; 6:23). This leads to a very important question: How are you going to be righteous?
2) Righteousness is empowered by Grace.
First of all, righteousness is imputed to us by grace and then it's imparted to us by grace (Gen. 15:6; Rom. 4). So righteousness is defined by law and empowered by grace. We can't keep the law and therefore we must throw ourselves on the mercy of God. His holiness becomes ours through imputation (2 Cor. 5:21). By and through God's sanctifying grace we are empowered to keep the law of God and grow in godliness. The fruit of faith and love is obedience (Eph. 2:8-10). This transitions us perfectly into a third key principle.
