Bend

A bend means pushing or pulling a fretted string perpendicular to its length to increase its tension, and therefore its pitch, without moving to another fret. A "whole-step" bend makes the note sound as if it were played two frets higher, without ever fretting there.

The real challenge isn't pulling the string, it's stopping at the right spot

Anyone can make a note's pitch move by pulling a string; what separates an accurate bend from a sloppy one is landing exactly on the target pitch and not beyond it — a "whole-step" bend that overshoots or undershoots sounds immediately off, even to a listener who couldn't explain why.

The technique sheet whole-step bend calibration works on exactly that accuracy, comparing the bent note to the same note simply fretted two frets higher.