hello, plz help me understand the system of adsense channels. how do we use channels? what are they for? thanks
If you have few websites, you can use URL channels because they are easy to setup. They will tell u that which site or URL has brought how much impressions, revenue etc.
Channels are, to identify the traffic source and revenue, if you own multiple sites use a unique channel for each website. If put the adsense code without including a channel, you won't know, which website is bringing the best traffic and revenue. In other words it's a kind of tagging.
a simple Learn how to setup Adsense Channels published in my blog a while ago may help you to better understand your own adsense channel system
visit this link: https://www.google.com/adsense/support/bin/answer.py?answer=9868&ctx=top5 the official page about adsense channel.
did u look at the small howto i wrote ? to understand channels you have to THINK advertiser 50% and the other 50% your own needs then you enjoy definitely much higher success in adsense I use the full quantity of channels ( 200 ) very successfully to optimize revenue and to optimize channel targetable ad-units for advertisers as well