Popular services such as Facebook, Instagram and Google offer tools for people to download the data they have on you.
Facebook offers a handy tool which visualises this data in your browser, so you won't need to download it.
To understand what type of data you get, let's unpack the Instagram data download. You will get information about:
By downloading this information you get to see how algorithms see you. Lines upon lines of JSON code, which help the algorithm to curate content specifically for you.
Subvert the algorithm, take back your data.