The Discrete trail consists of three components. The SD (this is the antecedent), the Response (this is the behaviour of the learner) and the reinforcing stimulus (this is the consequence that happens immediately after the behaviour).
If done correctly, the teaching process gives the learner a good foundation of how to carry out the new response, in mass trials. It builds on that foundation by challenging the learner with a mix of previous knowledge in discrimination training. Finally, it consolidates learning to achieve mastery.