Model

That wording is College Board's own. It comes from the appendix printed at the back of all four course descriptions, Vocabulary and Definitions of Important Ideas in AP Physics, which adds that a scientific model can be thought of as the set of rules that describe a physical phenomenon, and that the model sets out the boundaries within which the scientist will consider that phenomenon.

The boundaries are the whole idea. The appendix works its own example: a block released at the top of an inclined plane. A full account would need friction, air resistance, the slight increase in gravitational field as the block slides downward, and energy lost to vibrations, sound and thermal energy. Introductory physics discards all of it on purpose, to reach an answer within the accuracy the course needs.

The defaults are written down, so you do not have to guess. For AP Physics 1 the appendix lists five things you may assume unless a question states otherwise: frames of reference are inertial, air resistance is negligible, frictional and drag forces are negligible, edge effects of charged plates are negligible, and strings, springs and pulleys are ideal.

The appendix also says the AP Physics Exam will not directly assess understanding of physics vocabulary. You will not be asked to pick the correct definition of acceleration, or to state the difference between a system and an object. You are expected to use the words correctly in context.

A model is the decision; a representation is how you communicate it. Treating a thing as an object, or grouping several things into a system, are the two modeling moves AP Physics uses most.