Definitions: O

What is Offline?
Offline or off-line is anything not connected to a network, such as the World Wide Web.
What is Online?
Online or on-line is anything connected to a network.
What is the Open Directory Project?
The Open Directory Project (also known as Dmoz) is the largest human-edited Web directory with over 4.7 million web sites, reviewed by a global community of over 89,000 volunteer editors. The Open Directory was founded in the spirit of the Open Source movement, and is the only major directory that is 100% free. There is not, nor will there ever be, a cost to submit a site to the directory, and/or to use the directory's data. The Open Directory data is made available for free to anyone who agrees to comply with its free use license.
What is Opt-in Email?
Opt-in or optin email is email that recipients have previously requested by subscribing at a Web site or via email.
What is Opt-out Email?
Opt-out or optout email is similar to opt-in email, except that the email recipient is automatically added to a mailing list, unless they chose not to subscribe.
What is an OS?
An OS (Operating System) is a program that provides the basic functionality of a computer. For example, Windows, MacOS and Linux are all operating systems.
What is Out of the Box?
Out of the box is a synonym for 'off the shelf' meaning a ready-made software, hardware, or combination packages.
What is an Outbound Link?
An outbound or outgoing link is a link leading out of a site to another site.