What is the connotation of the words "Normal" and "Abnormal"? What is the intended effect?

In relating to behavior, normal means ordinary. Someone who displays normal (and usually healthy) behavior like the majority of people. Abnormal behavior is just the opposite.

For example: Person A sees a poisonous snake. They get away from the snake in fear. This person has normal behavior. Person B sees the same snake. They get on the ground and play with the snake. This person has abnormal behavior.