Definition of terms:

List size: Your number of subscribers.

Open rate: The percentage who open your emails (on average).

Ad click rate: Also known as the adCTOR (or ad click-to-open ratio) is the percentage of users who click on your ads — out of the set who have opened your email. For instance, if you have 100 subscribers, 30 open, and 6 click, your ad click rate is 20% (6 / 30).

Rate card: A rate card is a list of prices a media company charges for different ad units. Think of it as similar to a car's "sticker price"—this is the listed price, but there is room for negotiation between you and the potential sponsor.

Main sponsorship: Or "logo sponsorship." This is the primary sponsorship in an email newsletter, typically consisting of a logo at the top of the newsletter (near the newsletter's own logo or header) and a sponsored item about the advertiser somewhere in the body of the newsletter.