Detailed Breakdown: Redox
Redox as Electron Transfer: Oxidation is the loss of electrons; Reduction is the gain (OIL RIG). These processes always happen simultaneously. Oxidation states are a system designed to track these transfers, even in covalent reactions where electron movement is subtle.
Electrochemical Cells (Voltaic): These cells convert chemical energy into electrical energy using spontaneous redox reactions ($\Delta G < 0$). Electrons flow from the Anode to the Cathode through an external circuit, providing a portable source of power like a battery.
Electrolysis and Non-Spontaneous Processes: Electrolysis uses an external power source to drive non-spontaneous reactions ($\Delta G > 0$). This is the primary industrial method for extracting reactive metals like Aluminum and for electroplating protective coatings onto jewelry and tools.