SolidNotes blog has a very good article about the differences between Bend Tables and Gage Tables in SolidWorks.
Bend tables were the original table used by SolidWorks to pull Bend Deduction, Bend Allowance, or K-Factor values for use in calculating the flat pattern. Before the introduction of gauge tables, you would need a separate table for each thickness of material. Since gauge tables were introduced, data for multiple thicknesses of one material can be used in a single table; this makes life much easier!