Electrochemical Impedance Spectroscopy (EIS) is an analytical technique widely used in electrochemistry. EIS is being commonly used by researchers in biosensor development, corrosion study, battery, solar cell and fuel cell performance measurement etc. Due to the availability of high precision analog-to-digital and digital-to-analog converters available on microcontroller chips at low costs, EIS based purpose-built consumer electronic devices becoming more commonplace now. This tutorial paper presents the essential theoretical knowledge to understand the EIS and how the practical parameters are selected for an EIS measurement for a novice. The theoretical explanation of EIS is followed by a section with examples of the use of EIS in electrochemical biosensor development and performance measurement of batteries. This paper finally concludes on the advantages of the use of EIS as an analytical technique.