it puts 1 minute of timecode on the tape, this way, when you start recording useable footage, you dont have anythign too close to the begining of the tape. Dropouts, and debris will cause problems within the first minute of filming. this way the heads get to roll for a few seconds and it can help clear up any crap settled on the heads. Also when you batch cpture in your editing program, it often over winds the deck to get a 10 second pre roll before it starts capturing. if you have useable footage at the very start of the tape, it sometimes confuses the computer, and it will sit there and try to rewind back before 00:00:00:01 hours on the timecode. but obviously it cannot.
also, try usiing the Search function in the upper right corner. its helpful for stuff like this. Jus ttype "colorbars" or somethign and it will show you all the threads that involve color bars. this way you can learn about it all at your own pace.