Most of the analytics peeps keep talking in their jargon, one of the favorite is A/B Testing. The marketing folks most times start wondering what are they talking about.
A/B testing is essentially testing creatives - for the campaign. This could be applied to almost any form of advertising - Display, Site, Newsletters. The basic principle is keep an even split among all the creatives and try to measure the impact on the action - click through rate or conversion event. Some people think it is for only 2 creatives but one can use it for multiple 2,3, 4,5....
One important thing is that the sample size - it should be big enough to provide statistically significant results (t-test).
The first time I did a A/B test was a HomePage design for one of my clients. We were trying to measure which one of the two HomePage designs drove higher consumers to better use the entire website. Typically, on a Homepage you want information for existing customers, knowledge center and an acquisition section (to attract new customers). The banking websites do a pretty good job of this.
Since, then I have tested multiple forms of creative (display), emails (different forms of emails newsletters and then measuring the call to action rate), websites.