Public order refers to the normal standards and operations of society.
In the context of the law, crimes against public order are crimes that cause a disturbance to or violation of this order. Prostitution, public drunkenness and drug use are all considered to be crimes that are against the public order.
Public-order crimes are often victimless; they are simply acts that go against what is viewed as appropriate in society. Minor public-order crimes often have less severe sentences than other crimes such as armed robbery or assault, where there are actual victims.
What constitutes a public-order crime can vary significantly as time passes. For example, marijuana use has been decriminalized in many states in America. However, it was formerly viewed as a public-order crime in many of these places.