Explain the Ainsworth experiment 'strange situation'

Strange situation was a experiment conducted to study attachment behaviours in infants. The experiment was conducted in a regulated environment and children were taken in with a parent. The parent played with the child, then a person who is not known to the child would enter. The parent would leave, and the infant would be alone with the stranger. The parent returns to the room and comforts the child and then the child is left alone. The stranger returns first and then the parent. The childs behaviour is observed by the researchers and studied.
4 different behaviours of the child are studied, these behaviours helped the researchers to find out what type of attachment the child had. The types were Insecure Resistant, Insecure Avoidant and Secure. Insecure resistant children tend to be clingy, they find separation very upsetting and when their parent came back they may be angry at them for leaving. Insecure avoidant children were more independent, they didnt react negatively to be left and treated stranger in a similar way to parents, when parents returned they did not show relief or distress. Secure children explored when parent was there, were cautious of the stranger, were distressed when the parent left and comforted on the parents return.