With the addition of ad groups, now you can:
Assign budgets and targeting to ad groups
Since each ad group can contain multiple Pins, this allows for better control when testing your performance against various targets and objectives.
Align campaign budgets with marketing initiatives
Want to set a budget for a certain geographic region, product line or audience target? Ad groups make it easier to manage specific budgets within a single campaign, while still maintaining lifetime spend caps at the campaign level.
Streamline your campaigns across platforms
You may already be using something like ad groups on other platforms, so it may be easier for you to plan and manage all your campaigns in a familiar way.
What you need to do
You'll see notifications in Ads Manager and receive an email when ad groups are available. Then you’ll need to review campaigns with more than one Pin in Ads Manager and choose how you want to distribute your existing campaign budget across the ad groups. Campaigns with just one Pin will have only one ad group, so those budgets migrate automatically.
For more details, visit our Help Center to learn how ad groups affect Promoted Pin campaigns and tips on using ad groups to do more with your Pinterest ad campaigns.
—Dan Marantz, currently saving ideas to kids breakfast ideas