The only information that you need give is an email, username, and password. The username does not need to be your real name. Therefore, any personal information, beyond an email address, you choose to give is not compulsory.
If you choose to enter a real name in your preferences, this will be publicly available. However, this field is optional and there is no requirement for any user to give a real name.
Information from our server logs may be stored and used to gather aggregate data about users, and used to determine whether the identity of one or more users is the same in cases of abuse. This data includes your IP address, and details about your browser.
Edits by users who are not logged in will show the user's IP address in the page history of the article they edited, and also in other places on the site, including watchlists and recent changes, and in any external feeds made of such pages.