Attachment refers to the affectional bond between two people, especially the bond formed between infants and their caregivers. This bond is important for survival as it ensures close proximity and helps infants feel secure. Psychologists have identified phases of attachment development from birth to one year, including an indiscriminate phase where infants respond to anyone, and a specific attachment phase where infants show preference to familiar caregivers. Mary Ainsworth studied infant-caregiver attachment through her "Strange Situation" experiment, identifying secure, anxious-avoidant, and anxious-resistant attachment styles based on infant behavior when separated from and reunited with the caregiver. Long-term effects of early attachment on future relationships are also explored.