Ad Manager lets you promote your items so they appear on the homepage or at the top of the browse page
Once you have promoted an item - you can see the total impressions (views) it has gotten. The total budget for the campaign, how many people have clicked on it, and how much has been spent so far.
Impressions: The number of times the item has been shown to users (views)
Clicks: The total amount of clicks that your item has received. This means they viewed your item
Total Spent: The amount of clicks X the CPC price. (5 clicks X 0.10) = 0.50 spent.
CPC price: The cost per click that you set. If automatic it will adjust every day according to the average CPC so that your ad stays within the ads being displayed. If your CPC price is too low, the ad won't be displayed as other promoted items will have a higher CPC.
Edit or cancel your ad:
Here you can edit your ad settings such as CPC and other things. Or you can cancel your ad completely and get refunded the ad credits into your account.
Note: You cannot refund the ETH paid for the ad - but you will get the USD value credited to your account so that you can run other ads without having to pay again.
For more information on how to create your 1st ad, head over here.