"In many aspects of modern society, administrative law plays a powerful role and can be more immediately relevant to day-to-day legal practice than either statutory or judge made law." Kent C. Olson, 160. It’s because administrative agencies act in a wide range of subject areas, using various types of laws. You should ordinarily consider the possibility that there is some administrative law relevant to your problem. So, attorneys will find it impossible to practice law without needing to research administrative laws.
Then, what is administrative law? Administrative law is narrowly defined as law made by agencies within the executive branch of government. According to its authority from enabling statutes enacted by the legislature, an agency may promulgate rules or regulations, adjudicate matters within its purview, and perform characteristically administrative functions such as conducting investigations or granting licenses.
In a broad sense, it covers laws made by agencies in other branches.; further, statues and cases.