The Facebook Conversion API option is a tracking and analytics tool used to measure the effectiveness of your advertising by understanding the actions people take on your website. You can use this data to:
Reach the right people.
Find new customers, or people who have visited a specific page or taken a desired action on your website.
Drive more sales.
Set up automatic bidding to target people who are more likely to take actions you care about such as making a purchase.
Measure the results of your ads.
Understand how successful your ad is by seeing what happened as a direct result. You can view information like your conversions and sales.