Basically it means how much voltage you can put into a cell(s) before the charge stops. For example, I have an older Tekin BC112c and it has several charge profiles, such as P1 which allows the voltage to cutoff within .03-.05 volts of a full charge. Then, there's the P2 charge which allows the charger to cutoff around .06-.08 volts of a full charge. Those numbers are for the 6 cell pack, not individual cells. The only thing voltage threshold is for is to allow you to tailor the charge to acquire peak performance from a pack. For Ni-Mh batts you might want something with a very low threshold and for Ni-CDs you'd want something a little higher due to the difference in charge methods needed for top performance. Hope this helps without being too difficult to understand.