Deviance refers to behavior that departs from social norms and expectations, ranging from minor transgressions to serious crimes. There are two main types - formal deviance which violates laws, and informal deviance which contravenes unwritten social norms. Several theories attempt to explain deviance, such as strain theory which argues it results from a lack of legitimate means to achieve goals, and labeling theory which suggests deviance arises from societal reactions to certain behaviors. Deviance is socially constructed and dependent on cultural and historical contexts, so what is considered deviant can vary widely.