As Jantzen mentioned depends on what you are doing. The basic ones we see a lot of usage is A4T (Analytics for Target) which connects Analytics to Target so you can use Analytics report suites which is how we hold the data with Target as the destination to record your results.
Another great one that gets a ton of usage is Profiles & Audiences what this does is link up Analytics, Target, Audience Manager or sometimes just Audience Library connecting them together so that you can use historical data from Analytics for segmentation to get a specific audience out that you want to exam like for an example maybe the age of a group of people watching a specific show or looking at web page for a specific menu they clicked on. You can add in Campaign into this mix if you so desired the idea is then once you have identified this group that you want to target you can use Campaign to mail blast back to them for special offers or perhaps a follow up to a campaign out there for a second chance.
Does that kind of help with what you are looking for?