O&O
Owned and Operated. These are the local affiliates of major networks that run in your area. These stations probably include FOX, ABC, CBS and so on.

OAR
Original Aspect Ratio (1.85, 2.35, etc) This is the width-to-height aspect ratio. All HDTV programming is at 16x9 OAR. If it is not, it is not considered *true* high definition. If a signal is sent with black bars on the top or bottom (letterboxed), and is still in a 16x9 format, then it is considered HDTV.

OOM
Out Of Market. These are stations that are broadcast somewhere outside of your local metro area. There are two ways to get an OOM station. The first is if you can not receive a grade B signal from an affiliate of a major network at a height of 30 feet above average terrain. The other way to get that channel OOM is if you can receive a grade B signal from one or more local stations. In this case you have to get a waiver from each of the stations before you will be granted access to that OOM Channel.

Optical Digital Audio Output
This is a fiber output that uses a Digital Optical Audio cable to transmit audio from a DVD Player or Receiver to a receiver, television, or amplifier.

OTA
Over The Air. This is the signals you might pick up from your local ABC or CBS affiliate.