Let’s say you have a Facebook page and a web store.
You can public your products in Facebook creating a shop. So every single product on Facebook shop will redirect the visitors on the web store; on that product’s page.
A Facebook pixel is an analytics tool that consists of a code that you can put on your website. The pixel fires to track site visitors. This data allows you to retarget those users with Facebook ads in the future, as well as see what they’re doing on your site when they return. This allows you to gain more insights about your audience, send targeted messaging to users who already know your brand, and track the effectiveness of your paid social advertising efforts.
So adding some simple code you can monitor if someone added a product, purchased or search, viewed a category or a content.
Here the documentation (take a look at the section For Websites using Facebook Pixel)
https://developers.facebook.com/docs/marketing-api/dynamic-product-ads/product-audiences#associate-signals-to-catalog
