Google AdSense is Google's online advertising program in which advertisers agree to have their ads placed on websites and blogs that contain content that's relevant to the advertiser's business. For example, if you had a blog on cars, those who were advertising items related to cars, such as accessories and car parts would want to advertise on your blog.

With Google AdSense, Google does all the work for you. If you don't like one or more advertisers whose ads are being placed on your blog, you can block that advertiser from having ads displayed on your blog.