how does a simmerstat work?

what are wiring makes on the back of the simmerstat what do they mean

rob lowe
March 2011

http://www.emkayheaters.com/simmerstat.html

Chops up the power into On/Off/On/Off intervals - if the On periods are same as Off periods then you get half power - Quarter On and three quarters Off then Quarter power etc etc. Avoids full load current passing through contact points and early failure of thermostat.

Peccavi
October 2009