One of the definitions on the Merriam-Webster dictionary for scaffold is a supporting framework.
Wikipedia defines scaffolding as a temporary structure used to support people and material in the construction or repair of buildings and other large structures.
Based on these definitions, the training wheels on a bicycle, is an example of scaffolding. They are adjustable and temporary and provide the child with the support they need while learning to ride a bike with 2 wheels. Having the training wheels make the complex task of pedaling, balancing and steer (all at the same time), much easier until the child can do it on its own.
Scaffolding can also mean that a large task can be broken down into smaller tasks (to make it easier to accomplish).
In education, scaffolding is an instructional technique where the teacher models the desired learning strategy/task, and then gradually shifts responsibility to the students, whether is by giving more support at the beginning and gradually taking it away (training wheels) or by learning something in smaller steps.
Scaffolding can also be used to help your children develop certain physical, cognitive or linguistic skills. Imagine your child is playing with a musical toy for the first time. Parents usually show the baby where the buttons are so it can turn on the music. Then, you expect the child to ‘learn’ how to do it on their own. If they can’t do it, you might point to the button, and hopefully the child now learns it. This might have to happen a few times before the child knows what to do. That’s exactly what scaffolding is. The parent gave more ‘help’ at the beginning and gradually moved the responsibility to the child.
Scaffolding gives the child a context, motivation, or foundation to understand the new information. Having success from the beginning makes the child have some interest or curiosity in the task presented. Also, breaking a complex task into easier, more “doable” steps facilitates success.