Google Adsense is a contextual advertising program deisigned to generate revenue for the publisher. Ads are placed on your web site displaying content relative to your content. Each time one of these ads are clicked you earn a percentage of the revenue that Google makes from charging that particular advertiser. You can make money on a CPC (cost per click) and a CPM (cost per thousand impressions) system.

To join Adsense you will need to have an already running website or blogger blog (if you do not click here). Now you have a working website or blogger blog you can now sign up by clicking the adsense link on this page. Click on the "Click here to apply" button to sign up. Approval should take between 24 and 72 hours.

If your application was rejected this can mean a few things.
1. Make sure your site doesn't breach any of the terms and conditions.
2. If your site does not meet one or more of the pre-requisite, fix them and resubmit your application.

If all alse fails contact Google and they should happily help you out

How much you will earn is not always known. You could make zero or you could make thousands of dollars per month. If you have a successful website you could be earning alot of money but the best way to see how much you will make is to sign up and start advertising.