Elements defined by parameters - one change updates everything. The term that explains why Revit is not "AutoCAD in 3D". In parametric modeling every element is defined by parameters - dimensions, materials, rules and relationships - rather than frozen lines. Change one parameter and the element updates along with everything that depends on it: move a wall and the doors, dimensions and quantities follow.

This is what makes a BIM model smart rather than just drawn: geometry and data stay linked, and the model keeps itself consistent through every change.