You know how at school, the teachers and the principal made up the rules and you had to follow it? Such authorities also exist for many industries and they could be government controlled or put together by a leading industry group. These rules are also known as regulations and practitioners must follow it or risk fines or other serious legal, financial and reputational consequences.
For example…
Let’s say that Paul has set up a pool swimming fencing business. In Australia, there are regulations around the particular characteristics of swimming pools including the pool fence height, materials used et cetera. For every job that he is contracted to, he must make sure that the fence he builds meets these regulations.