What does sensitivity and specificity mean?

Sensitivity and specificity are statistical measures. They help in the evaluation of binary classification tests (tests with only 2 possible results).

Sensitivity measures the proportion of true positives that are correctly identified as such (e.g., the percentage of sick people correctly identified as such).

Specificity measures the percentage of true negatives that are correctly identified as such (e.g., the percentage of healthy people correctly identified as not sick).