Providing support just above the student's level. Then the support is gradually reduced, so they learn to do it independently. Scaffolding is the adaptation of teaching to the individual level of the student. It is also known as the zone of proximal development. What you can do independently is the actual development. What you need help with is the proximal development. The area in between is the zone of proximal development: activities that you cannot yet do independently, but can do with social support during their execution. By addressing students in this area, you activate the brain and thereby promote active learning. The support can, for example, be provided by guiding the level of direct instruction, the complexity of an activity, or the requirements set for an assignment. Students thus enter a state of flow. By gradually reducing the support ('fading'), students learn to do it independently.
Beed, P., Hawkins, M., & Roller, C. (1991). Moving learners towards independence: the power of scaffolded instruction. The Reading Teacher, 44(9), 648–655.