Burglary is generally the unlawful entry of a building or structure to commit a felony criminal offense (crime), theft, or assault. The definition of burglary varies from state to state (and in the federal system), and some states have different degrees of severity of the burglary offense—depending on the nature of the unlawful entry (type of building or structure), the intended purpose, and the illegal action taken by the defendant once inside the building or structure. In some states, breaking into an automobile, a coin-operated machine, or an ATM (automated teller machine) with the intent to commit a theft may also constitute the crime of burglary.

In California, burglary is defined under Penal Code Section 459. The state distinguishes between first-degree and second-degree burglary. First-degree burglary, also known as residential burglary, involves the unlawful entry into an inhabited dwelling with the intent to commit theft or any felony. This is considered a felony and is punishable by imprisonment in state prison. Second-degree burglary, also known as commercial burglary, involves the entry into any other type of building, vehicle, or structure with similar intent. Second-degree burglary can be charged as a misdemeanor or a felony, depending on the circumstances and the discretion of the prosecutor. Additionally, California recognizes the concept of 'burglary tools' under Penal Code Section 466, making it a crime to possess certain tools with the intent to commit burglary or any form of unauthorized entry.