Theft is the broad crime of stealing something that belongs to someone else, however it happens. Burglary is narrower: it specifically means breaking into a building or vehicle with intent to steal. Shoplifting is theft but not burglary; climbing through a window to take a laptop is both.
The core difference
Theft covers stealing in general, while burglary is the specific act of breaking into a building or vehicle to steal.
- theft — stealing something that belongs to someone else: He was arrested for theft after being caught shoplifting.
- burglary — breaking into a building or vehicle with intent to steal: Police are investigating a string of burglaries in the neighbourhood.
How to tell them apart
Every burglary involves theft, or at least the intent to steal, but not every theft involves burglary. Theft is the umbrella term: it just means taking something that is not yours. Burglary adds a specific extra element, unlawful entry into a building or vehicle, which is what makes it a separate, and often more serious, crime.
The mix-up tends to happen because news reports often use the words interchangeably when describing a break-in. A useful check: if nobody broke into anywhere, it is theft rather than burglary, even though the property was still stolen.