The oral stage is the first phase of Sigmund Freud's psychosexual development theory, occurring from birth to about 18 months. During this stage, infants derive pleasure and satisfaction primarily through activities involving the mouth, such as sucking, biting, and chewing. This stage is crucial for developing trust and comfort as babies interact with their environment. Successful navigation of the oral stage can lead to a sense of security and a healthy personality. Conversely, fixation at this stage may result in issues such as dependency or aggression in adulthood, often manifesting in behaviors like smoking or overeating.