working electrode
On a stage of three electrodes, the working electrode is the lead actor — it is the one where the reaction you actually care about takes place. While the others hold the voltage steady and carry the current, the working electrode is the surface where your analyte gets oxidized or reduced, and so it is the source of the signal you measure.
Formally, the working electrode is the electrode at which the analytical electrochemical reaction of interest occurs in a voltammetric or amperometric experiment. Its potential is controlled (relative to a reference electrode), and the current passing through it is the measured response. Common materials are platinum, gold, glassy carbon, and screen-printed carbon, each chosen for the potential range and chemistry it handles well.
It matters because the working electrode's material, size, and surface cleanliness shape sensitivity, the usable voltage window, and reproducibility — a fouled or pitted surface gives noisy, untrustworthy curves. The caveat is that it never works alone: in a modern three-electrode cell it is paired with a reference electrode (to set its potential accurately) and a counter (auxiliary) electrode (to carry the current), so the reference is not burdened by current flow.
A disposable glucose strip carries a tiny screen-printed carbon working electrode: glucose-derived electrons are collected there at a set voltage, and the current it produces — measured against the strip's reference and counter electrodes — becomes the blood-sugar reading.
The working electrode is where the measured reaction happens.
Working electrode (current-driven methods like voltammetry) is the counterpart of the indicator electrode (potentiometry, no current). Both are the 'sensing' electrode; the name just signals whether current flows.