ad.id: an unique ID for each ad.
xyz.campaign.id: an ID associated with each ad campaign of XYZ company.
fb.campaign.id: an ID associated with how Facebook tracks each campaign.
age: age of the person to whom the ad is shown.
gender: gender of the person to whim the add is shown.
interest: a code specifying the category to which the person's interest belongs (interests are as mentioned in the person's Facebook public profile).
impressions: the number of times the ad was shown.
clicks: number of clicks on for that ad.
spend: amount paid by company xyz to Facebook, to show that ad.
conversion: total number of people who enquired about the product after seeing the ad.
approved: total number of people who bought the product after seeing the ad.