Commercial Estimator temporarily saves the data you have entered on the data entry screens when you move to a different screen using the Sequential Navigation Buttons (at the bottom of the screen) and Random Navigation Links (on the left side of the screen). See Moving From Screen to Screen for further details.
The Save and Save as Random Navigation Links allow you to permanently save the estimate data as follows:
Save: Permanently save the estimate data, updating any previously saved data.
Save As: Permanently save the estimate data as a new estimate. When you select this option, Commercial Estimator asks you for a new Estimate ID. This option does not affect the originally saved estimate data.