Sensitivity and specificity are terms used to estimate the accuracy of test results.
Sensitivity refers to the probability of testing positive for a disease if the disease is truly present. As the sensitivity of a test increases, the number of people who have the disease but test negative (false negatives) will decrease.
Specificity refers to the probability of testing negative if the disease is truly absent. As the specificity of a test increases, the number of people who do not have the disease but test positive (false positives) will decrease.