Parametric drawing is a technology that is used for designing with constraints. Constraints are associations and restrictions applied to 2D geometry.
There are two general types of constraints:
•Geometric constraints control the relationships of objects with respect to each other
•Dimensional constraints control the distance, length, angle, and radius values of objects
The following illustration displays geometric and dimensional constraints using the default format and visibility.
In the design phase of a project, constraints provide a way to enforce requirements when experimenting with different designs or when making changes. Changes made to objects can adjust other objects automatically, and restrict changes to distance and angle values.
With constraints, you can
•Maintain design specifications and requirements by constraining the geometry within a drawing
•Apply multiple geometric constraints to objects instantly
•Include formulas and equations within dimensional constraints
•Make design changes quickly by changing the value of a variable
For more information, refer AutoCAD manual.