Criminal offenses under state and federal laws are generally categorized by the seriousness of the crime as felonies (more serious) or misdemeanors (less serious). Felonies are offenses that generally may result in prison sentences of more than one year, and misdemeanors carry sentences of one year or less. The United States Congress sets the penalties for all federal criminal offenses, and thus decides which criminal offenses are felonies and which are misdemeanors. And the state legislature in each state decides which criminal offenses are felonies and which are misdemeanors under state law.

In Illinois, criminal offenses are classified as either felonies or misdemeanors based on their severity, with felonies being the more serious category. Felonies in Illinois are punishable by imprisonment for more than one year, and they can include crimes such as murder, rape, and robbery, among others. Misdemeanors, on the other hand, are less serious offenses and typically carry penalties of up to one year in jail. Examples of misdemeanors include petty theft, simple assault, and some DUI offenses. The classification of crimes and the corresponding penalties are determined by the Illinois General Assembly, which enacts state statutes to define criminal conduct and set sentences. At the federal level, the United States Congress is responsible for defining federal crimes and penalties, including the distinction between federal felonies and misdemeanors. Federal felonies often involve violations of federal law that cross state lines or impact federal interests, and they are prosecuted by the United States Attorney's Office.