Point your phone at a street and arrows appear on the sidewalk showing you where to turn. That is augmented reality — overlaying digital information onto the real world. Unlike virtual reality, which replaces your surroundings, AR adds to them. You still see the real world. You just see more.

The technology dates back to the 1960s, but it reached consumers with games like Pokémon Go and filters on social media. Industrial AR is less visible but more consequential. Technicians use headsets to see repair instructions overlaid on the machine they are fixing. Surgeons preview tumors projected onto a patient's body.

How it works

• Cameras capture the real scene
• Sensors track position and orientation
• Software anchors digital objects to real locations
• A display combines both layers

AR still faces hurdles. Tracking must be precise. Headsets can be bulky. Battery life is limited. But as phone cameras improve and glasses get lighter, the line between digital and physical keeps thinning.