What does the Terzaghi weighting option do?

The Terzaghi Weighting only affects the apparent concentration of poles shown on contour (and rosette) plots.  The Terzaghi weighting does not change the location of the poles, which represent your raw data.

You can obtain the actual Terzaghi weighting factor which has been applied to the poles by using the Save Processed File option.  This allows you to save a processed version of your Dips file.  If you select the Terzaghi weighting checkbox in the dialog that appears, the processed file will contain an extra column with the actual Terzaghi weighting value which has been applied to each measurement.