With any economic transaction, there are three elements involved: 1) The Consumer; 2) The Producer; 3) The Product.
Whenever you receive something for free, ask yourself where you fit within the three elements of the transaction. Don’t assume you are the consumer.
Facebook (and similar social media) is free, and most people who use Facebook assume they are the consumer of the product. But, the consumer is always the one who is paying a price. Who is paying Facebook? How does Facebook make money? It makes money through advertising. So, the consumers of Facebook are those who are paying for ad space on the platform.
If the producer is Facebook, and the consumers are those paying for ads, what is the product?