Over the years, the clear leader in online advertising has been search engines. The major reason why advertisers allocate more than 40 percent of their online budgets to this medium is based on the likelihood that the user's need for immediate gratification is high. Whatever users type into a search engine, most of the time their behavior indicates a direct need.

For years, display advertising has been among the most prevalent online ad alternatives to search engine marketing, but it may not truly reach the advertisers' target audience. Consequently, advertisers have gotten used to being held accountable by measuring the direct success rates of their online ad campaigns. The arrival of behavioral targeting (BT) has advanced a search campaign's ability to give us the direct needs of consumers and has brought this ability to display ads.

After all these years of BT, I still find that our agency has to face ambiguity in the marketplace about what BT is all about. Whether it is among marketers, industry peers or publisher representatives, there is still some misunderstanding about terminology, discrepancies about how it works and a lack of knowledge about the different types of behavioral targeting.

For this reason, here's a little cheat sheet about behavioral targeting to clarify its function and impact within the online industry.

Author notes: Andreas Roell is CEO/president of Geary Interactive. Read full bio.