Tracking conversions allow you to measure the performance of each and every Facebook campaign, ad set an ad you are running by the website actions that matter to you. Within this, you'll be able to break down the data to understand the demographics, locations, devices and times that are driving your conversions.
At a basic level, this will allow you to manually dive into your data to understand how who and where your conversions are coming from, ensuring you can target your ad spend on the areas that will provide the best return.
At an advanced level—using a platform like Adgo—this will allow you to automate the optimization of your bidding and targeting towards multiple goals that are important to your business to improve your results in real time.
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Source: https://www.adgo.io/blog/2016/12/22/how-to-install-the-facebook-pixel-a-step-by-step-guide