system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What does our (user) data actually look like when it is tracked, collected, analyzed and sold?

I guess this is a multi part question. 

First kind of things do Google, Facebook, Reddit track and collect?  Is it on a per IP address basis, name basis?

Next, what does the data that look like when Facebook for example sells it to a third party? What kind of information is is available through Google Analytics?  Google doesn't sell its own data right, it just uses it to place ads for others right?

And then third parties who do research and analysis of this data, where do they obtain this data from and how do they analyze it and what can this data look like when it gets sold to their clients?

And how does one obtain such data freely and/or from these third parties?
gpt
Former ad tech guy here. Your data (cookie or otherwise) is stored and parsed into segments (male, twenties, white) which are used by ad campaign managers to appropriately target you based off of needs and wants for each ad campaign. Campaigns have a target sheet which tells each campaign manager (or computer, now) which segments to associate with that campaign. Your data is sold to numerous vendors, and in the case of ads, typically to an RTB backend who can do something with it.