In information technology, a product or system is described as open when its workings are accessible to the public and capable of being modified or improved by anyone. The alternative is a proprietary product or system.
The use of open in this context originated with the open source software (OSS) movement. Open source software refers to any program whose source code is made available for use or modification as users or other developers see fit. The software is usually developed through public collaboration and often made freely available, although that is not always the case.
Here are some examples of what open means in various other IT contexts:
Open security is an approach to safeguarding software, hardware and other information system components with methods whose design and details are publicly available.
Open content is material such as documents, images and audio or video presentations that may be freely and legally reproduced, edited, excerpted, expanded and republished.
A massive open online course (MOOC) is a free Web-based distance learning program that is designed for the participation of large numbers of geographically dispersed students.