The document discusses biosensors, which integrate a biological recognition element with a physiochemical transducer to produce an electronic signal proportional to the concentration of an analyte. It provides examples of common biosensors like those used for glucose monitoring and pregnancy testing. The key components of biosensors are described as the analyte, sample handling/preparation, detection/recognition, and signal analysis. Common sensing techniques include electrochemical, fluorescence, and optical methods. Applications of biosensors include medical diagnostics, food analysis, and environmental monitoring.