Many states define robbery as theft/larceny of property or money through the offender's use of physical force or fear against a victim. Where a deadly weapon such as a gun is used or the victim suffers injury, the robbery may be charged as "armed" or "aggravated." Unlike burglary, the crime of robbery almost always requires the presence of a victim who suffers actual injury, or is threatened with harm.
For example, Bob approaches Jim from behind, demanding Jim's wallet while pressing a hard object into his back. Fearing that Bob has a gun, Jim gives up his wallet. If Bob did use a gun, or if Jim suffered an injury, the charge would likely be elevated to "armed" or "aggravated" robbery.