Website Traffic
A good website is a poor investment without visitors. Traffic Ads drive visitors to your website. Visitors could become buyers of your products, newsletter subscribers etc.
Leads & Messages
Conversion starts with a message (or call) from an interested person. Some ads are measured by the number of people who reach out to you via direct messages.
Brand Engagement
Likes, Comments, Profile views etc. are metrics that validate your brand as engaging. Online branding involves putting out great content people find valuable.