Color bars are a standard that TV stations use to calibrate their equipment. In other words, the engineers play color bars to make sure that their equipment is showing red as true red, green as true green, etc.
Including them at the beginning of your video allows them to see if your video's color profile matches the TV stations.
They're usually accompanying by a tone (supposedly representing the audio level for your video, if you've used your audio meters correctly while editing) that allows them to set the playback audio level.
Calibrate your audio levels by watching the meters next to the Preview window. If you keep your audio from peaking beyond zero, your levels should match those of your bars and tone.
There is only one bars and tone that I know of. That's why it's a standard.
Once the tech at the TV station sees your bars and tone, he'll know what color profile the rest of your video is using.