This document provides an overview of biosensors, including their definition, components, principles of operation, examples, applications, and future potential. A biosensor integrates a biological recognition element with a physiochemical transducer to produce an electronic signal proportional to the concentration of an analyte. Common types include calorimetric, potentiometric, amperometric, and optical biosensors. Applications include medical diagnostics, environmental monitoring, food analysis, and industrial process control. The document concludes that biosensors can help identify materials and their concentrations in various fields.