Radio used to refer to signals broadcast through free space using electromagnetic radiation in the spectrum that we refer to as radio waves, consisting of everything from very long wave (high audio frequencies) which are used communicate with submarines under water to millimeter wavelengths just now starting to be used for short distance high speed data transmission.
In broad terms radio can transmit audio, video, data, facsimile, remote instrument data, and more. IN more common terms people are used to thinking of radio as bringing voice and music into their homes without wires.
Radio in the past has been a broadcast medium. That means that a signal is sent out that will be broadly received, received by many. It was such an expensive medium that a large audience was necessary to justify the expense.
In modern times it is now possible to originate a signal on the Internet that a number of people can listen to simultaneously from anywhere in the world that has internet connectivity. Because it is much less expensive to broadcast over the internet (netcast) verses broadcasting over the air, it makes it practical to target programming to much smaller audiences and thus many program subjects that would not have been able to garner a large enough audience to be commercially viable in the past, can exist on the internet.
For those of you that have an interest in the paranormal, one source of broadcasts on various paranormal subjects ranging from spiritual to UFOs to cryptozoology, is Paranormal Radio at http://www.paranormalradio.net/. You will need Quicktime to listen.
On Paranormal Radio you can listen to live broadcasts (there is a schedule at the website) or listen to various programs that they have archived.
If you know of other interesting radio on or off the net, write me at firstname.lastname@example.org, put “RADIO” in the subject so I’ll spot it amongst the spam, and I’ll get it up here for everyone.