Rules can be understood as ‘regulations’, which mandate correct, authorised, acceptable behaviours. In this sense, rules are external to those who abide by them, prescriptions of certain forms of a monolithic system as the ‘correct’ ones. 

Rules can also be understood as the ‘regularities’ which emerge from language use: actual patterns of knowledge which get mentally represented as a function of the personal histories of individuals, underpinning what they say, write or sign through experience rather than obligation.