On Truly Positive Bananas
Bob the baboon really likes bananas. He’s positively inclined to bananas. However, Bod disgusts apples. His view on apples is pretty negative.
Bob is an old baboon. He knows he cannot trust his vision anymore. His mouth is reliable though.
When Bob wanders through the jungle and sees a tree with bananas (positive) he becomes really happy. Usually, what he thinks is a banana (positive) is indeed a banana (true positive). By tasting the fruit he’s gonna find it out. If he’s unlucky, the beloved banana (positive) turns out to be an apple (false positive).
Conversely, Bob always approaches apple (negative) trees. You never know. He needs to taste the fruits to be sure. Maybe that yucky apple (negative) is in fact a banana (false negative). Pretty often, it’s an apple (true negative) and Bob rather bunks off.