First, no question is dumb, if you don’t understand…
OK, two end stops on the same end are used to re-zero the X axis that has the large carriage and two separate motors, one driving each end. When power is off, normally it is possible to move the carriage by hand, so one end could move getting it is likely for it to get ‘out of square’. Assuming the end stops are ‘square’, running the ends to the stops, simultaneously, should have both ends touching their respective stops at the same time. If they don’t, we keep driving the one that hasn’t touched till it does. Once both touching their own end stop at the same time, the gantry is ‘in square’.
Typically this is only done on the X or Y axis (the other axis and z only have one stepper so this technique isn’t relevant).
I hope this helps and the description is not to convoluted.