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.

A defendant generally commits the offense of burglary of a building or habitation (1) by entering a private habitation or any part of a building that was not open to the public, (2) without the consent of the owner, and (3) with the intent to commit a felony, theft, or assault.

A defendant may also commit the offense of burglary of a building or habitation by entering with consent, but remaining hidden with the intent to commit a felony, theft, or assault—or entering with consent and attempting to commit a felony, theft, or assault, or actually committing a felony, theft, or assault.

Some states make a distinction between burglary of a habitation (a place used for overnight accommodations) and burglary of a building that is not a habitation (home). Burglary of a habitation is usually treated as a more serious offense with greater penalties.

In Pennsylvania, burglary is defined under Title 18 § 3502 of the Pennsylvania Consolidated Statutes. The offense occurs when a person enters a building or occupied structure with the intent to commit a crime therein, unless the premises are open to the public or the defendant is licensed or privileged to enter. The structure does not need to be a dwelling for the offense to be considered burglary, but if it is, the offense is graded more severely. Pennsylvania law distinguishes between burglary of a habitation and other structures, with the former typically incurring harsher penalties. The intent to commit a crime must be present at the time of entry; however, actual commission of the crime is not necessary for the charge of burglary. The offense is generally considered a felony of the first degree, but if the building or structure is not adapted for overnight accommodation and no one is present at the time of the offense, it may be downgraded to a felony of the second degree. Additionally, if the defendant is charged with entering a structure that is not a dwelling, and it is proven that the entry was made with the intent to commit a theft, the offense may be graded accordingly.