This document discusses the importance and meaning of test coverage in software testing. It defines test coverage as the total number of requirements tested divided by the total requirements in scope. Maintaining high test coverage is important for reducing unknown risks and meeting contractual obligations. Different types of coverage include test, project, release, design, and execution coverage. Tools like requirement traceability matrices can help measure coverage. The document also discusses approaches to test coverage in agile development, risk-based testing, regression testing, and interpreting coverage metrics and defect rates.