Ghostery is a tidy little bit of software that everyone in the display space should be using on a daily basis. It helps detect tags, pixels and beacons running on a particular site (maybe some of the WSJ reporters should have had this installed before publishishing their deomonising series on behavioural targeting). The tool can be downloaded as an app for the three heavy weight browsers, namely Internet Explorer, Firefox and Chrome. The company has a good insight into how the overly complex display eco-system is knitted together. And last week it published an interesting overview of what functions different intermediary companies carry out in the display marketplace. Below is a pretty definitive list compiled by the good people at Ghostery relating to area of expertise - but as the post points out there is some serious overlap in various disciplines. For instance you can be a data company (collect third party data) and also buy media, as is the case with many ad tech operations. It's an excellent summary - so commit to bookmark. You can read more about the company’s offering here.

1. Advertiser: A company sponsoring advertisement and ultimately responsible for the message delivered to the consumer. Example: DoubleClick

2. Exchange: A provider of marketplace connecting advertisers to ad networks and data aggregators (online and off), often facilitating multiple connections and bidding processes. Example: Right Media

3. Network: A broker and often technology provider connecting advertisers and publishers. (web site operators) Example: Burst Media

4. Online Data Aggregator: Collects data from online publishers and provides it to advertisers either directly or via exchange. Example: BlueKai

5. Offline Data Aggregator: Collects data from a range of offline sources and provides data to advertisers directly or via exchange. Experian

6. Publisher: Website operator who displays ads for advertiser(s) in various types campaigns. Example: The New York Times

7. Optimizer: Provider of analytics technology and services for ROI assessment and content optimization purposes. Example: ROILabs

8. Research: Collects data for market research purposes where no ads are serviced through this data. Example: Example: Safecount

9. Retargeter: Providers of technologies that allow publishers to identify their visitor when they place ads on third party sites. Example: FetchBack

10. Analytics Provider: Provider of cross-platform statistical analysis to understand market effectiveness and audience segmentation. Example: Google Analytics

11. Agency: Provider of creative and buying services (both audience and data) for advertisers. Example: MediaCom

12. Ad Server: Technology that delivers and tracks advertisements independently of the web site where the ad is being displayed. Example: DoubleClick DART

13. Demand-Side Platform: A technology provider that allows marketers to buy inventory across multiple platforms or exchanges. DSPs often layer in custom optimization, audience targeting, real-time bidding and other services. Example: Invite Media

14. Supply-Side Platform: A technology provider that allows publishers to access advertiser demand across multiple platforms or exchanges. SSPs often layer in custom yield optimization, audience creation, real-time bidding and other services. Example: AdMeld

15. Ad Verification: Certifies or classifies webpages in an effort to prevent advertisers’ campaigns from running on unsavory or blocked content, and/or protects advertisers from having other companies run their ads incorrectly. Example: ClickForensics

16. Online Privacy: Technology providers that deliver information and transparency to consumers on how 3rd party companies gather and use their data. Example: Better Advertising