From wikipedia: Conformity is the process by which an individual’s attitudes, beliefs, and behaviors are influenced by other people.
This influence occurs in both small groups and society as a whole, and it may be the result of subtle unconscious influences, or direct and overt social pressure. Conformity also occurs by the “implied presence” of others, or when other people are not actually present. For example, people tend to follow the norms of society when eating or watching television, even when they are at home by themselves.

People often conform from a desire to achieve a sense of security within a group—typically a group that is of a similar age, culture, religion, or educational status. Any unwillingness to conform carries with it the very real risk of social rejection. In this respect, conformity can be seen as a safe means of avoiding bullying or deflecting criticism from peers. Conformity is often associated with adolescence and youth culture, but it affects humans of all ages.

Although peer pressure may be viewed as a negative trait, conformity can have either good or bad effects depending on the situation. Driving safely on the correct side of the road is a beneficial example of conformity. Conformity influences the formation and maintenance of social norms and allows society to function smoothly and predictably.