Can you explain "Adgroup"?
To what GuitarZan has already posted, I'd add:
Think of an Ad Group as an ad (or ads) about a particular subject, and a collection of keywords - all highly related to that same subject - which cause the ad to show. In your account, you can create 2500 of them - 100 per campaign.
In other words, an Ad Group is your opportunity to be really, really targeted.
By the way, here is an online glossary of commonly used terms in AdWords:
[adwords.google.com...]
Where you will find Ad Groups defined in this way:
Ad Group - An Ad Group contains one or more ads targeting one set of keywords. You set a maximum cost-per-click (CPC) for an Ad Group keyword list or for individual keywords within the Ad Group.
AWA