Open source hardware is more or less same to that of the free and open source software, it got with it physical artifacts of technology and is distributed the same way as the FOSS. In here the information about the hardware is made available, that would include with it the hardware design, its schematics, PCB layout, mech drawings, hardware description language source code, and the other needful data for its implications.
Just like the free and open source software, as they target on proprietary solutions and commercial software vendors, the open source hardware does the same. The licencing it gives makes it possible for easy implication and use, and that makes it cost effective with no royalty and other fees that would be needed if it were not open source hardware. That means you can download the specifications to any open source hardware and then make the component or the hardware on your own.
Now one of the major harness of open source hardware we can see is the 3D printing industry, the big booming industry now itself and will touch much as $5.2 billion by 2020. With the open source hardware, here prototyping becomes much as easy as anything else. Helps anyone make prototypes, build them the way they want to let it interact with their inputs. Projects like RepRap, MakerBot feature on the additive manufacturing technology and make most of its own components. Own replicating ability makes it possible to make and redistribute the 3D printing machine itself and share it with other users or communities and letting them make the same or more of complex products. Helps to do all these by cutting the need to have costly industrial infrastructure. That means almost anyone can do 3D printing and replications, all in ease.