When the Reformed and Lutheran scholastics talked about God’s moral law (lex moralis), they taught that there are three basic uses of the law (usus legis). According to Richard Muller’s helpful research, they are:
1) The civil use (usus politicus sive civilis). That is, the law serves the commonwealth or body politic as a force to restrain sin. This falls under the general revelation (revelatio generalis) discussion in most of the scholastics as well as natural law (cf. Rom 1-2).
2) The pedagogical use (usus elenchticus sive paedagogicus). That is, the law also shows people their sin and points them to mercy and grace outside of themselves (e.g. Rom. 3:20). In Richard Muller’s summary, this is “the use of the law for the confrontation and refutation of sin and for the purpose of pointing the way to Christ” (p. 320 of Muller). This can be found in the Heidelberg Catechism Lord’s Days 2-4.
3) The normative use (usus didacticus sive normativus). That is, this use of the law is for those who trust in Christ and have been saved through faith apart from works (e.g. Ps. 119). It “acts as a norm of conduct, freely accepted by those in whom the grace of God works the good” (p. 321). This can be found in the Heidelberg Catechism Lord’s Days 32-52 – the law is a moral guide for those who have been saved by grace.
Note: “In this model, Christ appears as the finis legis, or end of the law, both in the sense that the usus paedagogicus leads to Christ as to a goal and in the sense that the usus normativus has become a possibility for man only because Christ has fulfilled the law in himself” (Ibid.). In other words, in both the pedagogical use and the normative use Christ is central as the one who has saved his people from the law’s demands and the one who has earned for them the gift of Spirit-wrought obedience.
You can read a bit more in Muller’s Dictionary of Latin and Greek Theological Terms.