Concerning classification in the field of AI, accuracy is a metric for measuring the quality of mostly binary classifications. It is calculated as the proportion of correct classifications in all classifications.
See also:ISO/IEC TR 29119-11:2020 performance metric used to evaluate a classifier (3.1.21), which measures the proportion of classifications (3.1.20) predictions (3.1.56) that were correct
ISTQB - CTAI Syllabus The ML functional performance metric used to evaluate a classifier, which measures the proportion of predictions that were correct (After ISO/IEC TR 29119-11)