The data it collects from your website or funnels can help you create better Facebook ads, optimize your ads, get more conversions, target better audiences, build targeted audiences for future use or for re-targeting ads, etc.
Let's suppose that you are running an ad on Facebook and you have the pixel installed all over the funnel steps or the website.
Then it will track what your customers are mainly doing in your funnel or website. Have they gone to the checkout page? Did they leave from the Order page? or How many of them have initiated checkout?, have they purchased, completed the registration, etc.
See how powerful the piece of code is!!!
After looking at all the data collected by the pixel, you can easily optimize your ads, create lookalike audiences, do re-targeting ads, etc.