Supercapacitors are efficient energy storage devices that offer high power density, long cycle life, and fast charge-discharge rates, making them suitable for applications requiring high power output, such as electric vehicles and renewable energy systems. However, their energy storage capacity is lower than that of batteries, prompting research to enhance their energy density. This review discusses the history, fundamental principles, and current developments in supercapacitor technology. Supercapacitors can be classified into electric double-layer capacitors (EDLCs), pseudocapacitors, and hybrid capacitors, each with distinct mechanisms for energy storage. EDLCs store energy through ion adsorption at the electrode-electrolyte interface, while pseudocapacitors rely on fast redox reactions. Hybrid capacitors combine the advantages of both. The paper also covers the main electrochemical measurement techniques used to evaluate supercapacitor performance, including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The review highlights the importance of electrode materials, electrolytes, and the synergy between them in determining supercapacitor performance. Current research focuses on developing novel electrode materials, such as carbon-based materials, transition metal compounds, and conducting polymers, to improve energy density and cycling stability. The paper also discusses the challenges and future directions in supercapacitor technology, emphasizing the need for sustainable and efficient energy storage solutions.Supercapacitors are efficient energy storage devices that offer high power density, long cycle life, and fast charge-discharge rates, making them suitable for applications requiring high power output, such as electric vehicles and renewable energy systems. However, their energy storage capacity is lower than that of batteries, prompting research to enhance their energy density. This review discusses the history, fundamental principles, and current developments in supercapacitor technology. Supercapacitors can be classified into electric double-layer capacitors (EDLCs), pseudocapacitors, and hybrid capacitors, each with distinct mechanisms for energy storage. EDLCs store energy through ion adsorption at the electrode-electrolyte interface, while pseudocapacitors rely on fast redox reactions. Hybrid capacitors combine the advantages of both. The paper also covers the main electrochemical measurement techniques used to evaluate supercapacitor performance, including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The review highlights the importance of electrode materials, electrolytes, and the synergy between them in determining supercapacitor performance. Current research focuses on developing novel electrode materials, such as carbon-based materials, transition metal compounds, and conducting polymers, to improve energy density and cycling stability. The paper also discusses the challenges and future directions in supercapacitor technology, emphasizing the need for sustainable and efficient energy storage solutions.