Statement coverage measures the percentage of executable statements that have been exercised by a test suite. Achieving 80% statement coverage means that 80% of the executable code lines have been tested. This metric helps in understanding how much of the code has been covered during testing. However, it does not guarantee branch coverage, variable initialization, or detection of all possible defects. The ISTQB CTFL Syllabus v4.0 explains statement coverage as a measure of the extent to which the code has been tested, without implying other types of coverage or testing goals.