Administrative law is the law that governs the administrative actions. As per Ivor Jennings- the Administrative law is the law relating to administration. It determines the organisation, powers and duties of administrative authorities. It includes law relating to the rule-making power of the administrative bodies, the quasi-judicial function of administrative agencies, legal liabilities of public authorities and power of the ordinary courts to supervise administrative authorities. It governs the executive and ensures that the executive treats the public fairly.
Administrative law is a branch of public law. It deals with the relationship of individuals with the government. It determines the organisation and power structure of administrative and quasi-judicial authorities to enforce the law. It is primarily concerned with official actions and procedures and puts in place a control mechanism by which administrative agencies stay within bounds.
However, administrative law is not a codified law. It is a judge-made law which evolved over time.