To get started you need an account with an external ID-provider (currently Facebook). The main reason for this, is to ensure the uniqueness of respective user. (See more reasons on Why using an IdP)
Integrity issues
The data taken from the ID-provider (Facebook) are name, image and email. Email is used to identify you even if the site switches to an other ID-provider. Name and image are used as default values for your convenience (you can change these in the settings).
No data is shared with the ID-provider (and nothing is written to your Facebook flow or anything like that).
How to delete accounts
Video: How to create an account, and then delete it.
A separate tool for continuous tracking. Allows you to switch show/hide on multiple trackers with a single button click (Handy when you want a lunch break etc)