There are two ways of advertising on Google:
Search network
Contents network
The Search network is where the current ads appear daily and these are for google and other search engines they supply – e,g, AOL, Ask
The Content network is non search sites and here you can target in two ways:
Keywords and contextual advertising where Google scans the text of the web page and determines what the page is about and then serves ads that match based on the keywords chosen. It is quite similar to the Search network except that impressions are way higher and CTR way lower. We recommend that search and content campaigns are kept separate so that statistics are more easily absorbed and understood.
Placement targeting puts ads where we choose on individual sites in the Google content network. Site sections can sometimes take that one step further by placing ads on only one section or even one page of a site but only if smaller sections of the site are made available for targeting by the publisher. These more specific placements offer more control and visibility into where ads will appear on sites in the content network.
In pacement targeted adverts there are four ways to identify sites and this is what detail you can get down to:
List URLs. Suggest websites on which to advertise. If the sites are part of the Google content network OK. If not, bad luck.
Describe topics. Enter topics that match content. Select from a list of placements that match those topics.
Browse topics. Look through categories like Entertainment and subcategories like Movies or Music. Click the category or subcategory that best matches.
Select demographics. Choose the audience to target by selecting from any or all the demographic categories provided. Audience gender, age and household income are among the demographic categories available for selection.
One gets a list of up to 100 available placements with a site's URL and the approximate number of impressions per day and whether the placement runs text, image or video ad formats.
Display likelihood gives a 'sneak preview' of the performance expected for an ad group, given the placements and default bid chosen for it but only with placement-targeted campaigns that have selected CPM and not CPC bidding. Display likelihood is estimated at the ad group level only, estimates are not available on a site-by-site basis.
Many factors determine how often an ad will appear, but the placements and the amount bid are especially important. Targeting highly specific sites and making extremely high bids of course ensures an ad will almost certainly appear.
Display likelihood displays one of these messages:
On both keyword and placement targeted content adverts one can use ads in the following formats and sizes, though not all are necessarily available on any particular site):
Text ads - standard 4 line and others
Image ads
Video ads



