On the Web, direct response usually refers to a clickthrough on an ad banner.
Many advertisers will audit the effectiveness of a campaign based on the number or percentage of direct responses. While this can lead to the hard-bargain, cost-per-click deals that almost entirely ignore the branding value of web advertising, evaluating response is often the best way to an honest audit of the product, advertising message, and ad placement.
The term “eyeballs” is a quaint reference to the number of people who see, or “lay their eyes on,” a certain advertisement. When buying radio time, marketers refer to “ears” instead of “eyeballs.”
If anyone who isn’t a network engineer mentions “hits” to you, they’re probably trying to pull the cyberwool over your eyes. Hits are the individual requests a server answers in order to render a single web page completely. The page document itself, the various images on the page, any other media files embedded there – each of these items represents a separate hit. In other words, the more GIFs used in a page, the higher the hit count – so while hits may be a good indication of poor page design, they won’t tell you much about traffic.
“Impression” is industry parlance for an actual ad viewed.
For example, there’s an ad on this page, so you’ve just accounted for at least one impression. Why thank you! Of course, it’s next to impossible to know if someone actually sees a given advertisement on the Web. After all, a user might not scroll down far enough to see the ad, could be surfing with images turned off, or might press Stop before the ad is fully loaded into the browser window. This can make impression-counting on the web a thorny endeavor, but then the same goes for other media as well (who knows whether people are actually watching the commercial or off in the kitchen getting another beer?). Short of guessing, you’re probably better off slaughtering a goat and examining its entrails.