Definition - What does Open-Source Hardware mean?
Techopedia explains Open-Source Hardware
Some good examples of open source hardware are Arduino boards. These boards are part of a complete open source electronics prototyping platform including a software development environment. A complete Arduino system is made up of both open source software and hardware. Because the supporting software of Arduino systems can be downloaded for free and the reference designs for the hardware are available under an open source license, people could easily create their own boards or build devices out of the Arduino software and hardware at a minimal cost.
Just like open source software (OSS), open source hardware uses licenses. A majority of these licenses are based on existing OSS licenses. Some of the widely used licenses for open source hardware include the TAPR Open Hardware License, Balloon Open Hardware License and the Hardware Design Public License.