Bulk eMail - Commercial email delivered without prior permission.
Co-Registration - A secondary offer advertised along with a registration. "Click here if you would also like to subscribe to the 'Daily Jokes' newsletter."
CPA - Cost Per Acquisition - The costs associated with generating a sale or lead.
CPM - Cost Per Thousand - The cost of 1000 advertising units (be it banner impressions, delivered emails, etc.)
CTR - Click Through Ratio - The ratio of people who respond to an ad and visit the advertised web site.
HTML - Hyper Text Mark-Up Language - A programming language that builds web sites or HTML based emails. Allows the inclusion of colors, images and response functionality to email. HTML based campaigns typically receive a higher CTR than text based campaigns.
Opt-In - Where an individual deliberately requests to join a service or receive more information.
Opt-In e-mail - Commercial email delivered with prior permission.
Opt-Out (a) - To unsubscribe to a service or ask to stop receiving information.
Opt-Out (b) - Where an individual deliberate requests to NOT join a service or receive more information.
Recipient - An individual who receives commercial email.
Registration - Process of subscribing to a service or becoming a member.
Targeting - Process of isolating an audience who is most likely to respond to you advertisement.
Text - A text based email, generally in "black and white." Functionality is limited to a web site link.