TV-out is commonly used to label the connector of equipment offering an analog video signal that is acceptable for a television AV input. It is different from AV-out in that it only offers video and no audio.
When the connector is an RCA connector (cinch) or a mini jack the signal is typically composite video. On many computers you may find an S-Video connector, offering an S-Video signal. It's recommended to use S-Video if possible, since S-Video offers better image quality than composite.
The TV-out signal is led through a cable to the TV where it is connected to the S-video, cinch or SCART connector of the AV-input. The TV has to be switched to the associated AV-channel to display the signal. In many cases you will have to switch on the signal on the source as well.