Campaigns
A campaign is made up of one or more ad groups that share the same budget, schedule and geo-targeting criteria. Typically, campaigns are created to achieve a marketing goal (for example, a summer clearance campaign, a new product launch campaign, or a campaign that targets customers in a specific geographic location).

Ad Groups
An ad group contains your ads (the marketing messages you created) and your targeting criteria (such as keywords). Your ads are rotated against your targeting criteria and are displayed to your potential customers. You can create multiple ad groups within a campaign.

Ads
Your ads are the marketing messages that your potential customers will see. An ad is comprised of the title, description and URL.

Keywords
A keyword is a single word or multiple-word phrase that relates to the products or services you wish to advertise. When potential customers are looking for information related to your keywords, your ads may be displayed.