Razor wire is a mesh of metal strips with sharp edges that are designed to prevent the passage of humans. The long-standing term "razor wire" is often used to describe barbed tape products. Razor barbed wire is much sharper than standard barbed wire; it's named for its appearance, but it's not razor-sharp. These tips are so sharp that they can rip and snag clothing and meat.
The multiple blades of barbed wire are designed to inflict serious injury on anyone trying to crawl through, so they act as a strong psychological deterrent. Barbed wire is used in many high security applications because while humans can bypass it relatively quickly with tools, penetrating barbed wire barriers without tools is very slow and difficult, giving security forces more time to do react.
From the late 1960s onwards, barbed wire was commonly found in prisons and secure mental hospitals, and the increased break-in time was a distinct advantage for poorly equipped would-be fugitives. Until the development of reinforcement barbed wire in the early 1980s (especially after the September 11, 2001 attacks), it was rarely used for military purposes or really high security installations because with the right tools it was easier than barbed wire sabotage. Since then, some militaries have replaced barbed wire with barbed wire in many applications, mainly because it is slightly lighter for the same effective coverage and it is less expensive than barbed wire or reinforced barbed wire. It takes up very little space when stored on the drum.
More recently, barbed tape has been used in more commercial and residential security applications. This is usually primarily a visual deterrent, as well-prepared burglars can break barbed wire and barbed tape barriers in a similar amount of time, using simple techniques such as cutting wire or throwing a rug over its strands.
Razor wire/barbed tape and similar fencing/barrier materials are prohibited in some areas due to their hazards. Norway bans any barbed wire unless combined with other fencing to protect domestic animals from exposure.