A popup or pop-up is an ad that is triggered as soon as the user clicks anywhere on the main page. This will open a new browser window appearing in front of the main page.
A popunder is an ad that's triggered when the user clicks anywhere on the page. This pop under appears behind the main page the user is visiting and remains "unnoticed" until the main browser is closed.
A new tab is triggered when the user clicks on the main page. Appearing in a front position immediately gets the user's attention to the advertisement.
A full page advertisement appears on the current web page which the user is visiting. This is an interesting way to capture the user's attention on the advertisment.
A simple link integration will present the advertisement. This format is usually used by publishers who are ready to open the format and send the user to your direct link.