Linux is perhaps the most famous example of open source technology. Linux refers to both an operating system kernel, and to the suite of software which surrounds it. See the article on open source for more information about the open source technology approach and its impact on businesses.
There are three broad categories of relevance for Linux:
Some companies such as Red Hat and Canonical distribute Linux operating systems directly and sell support. Others distribute environments based on Linux, such as Google's Android for cell phones and Chromium for netbooks and similar embedded devices.
Many enterprise software vendors develop software which runs on Linux (and sometimes other platforms), such as:
Many Internet-facing technology companies use Linux for their servers.
Many other technology companies will use Linux to power their devices.
Microsoft competes with Linux on servers and in the embedded device market. If Linux begins to gain significant market share on the desktop, it will affect sales of the Windows operating system.