Controllability
Some parameters are out of your control.  Examples include weather conditions, the quality or perhaps the rate of materials coming into your process or environmental parameters.  If you cannot control a variable, you can specify a value for it while optimizing.  If it is controllable, you can specify constraining limits on the values considered.

Desirability
For parameters in your control, you may desire that the optimization process comes up with certain values.  This is useful for finding solutions nearby where you are operating already, minimizing process disturbances changing from current conditions to optimal settings.

Costs
Some parameters are expensive, such as rare metal ingredients in product formulations or energy.  Accordingly, you can apply costing to your parameters so iImprove can find cost effective solutions.  Cost functions are linear with a fixed and variable component.

Next Step: Constraints