It is a string with a special format derived from a secure hash of content that you make up about yourself.
The links here can help lead you to tools that help open pages within your URL framework page enabling you to work with your personal preferences within those pages.
The pages you open may use personal data by asking your framework page to make requests on their behalf. For example, an e-commerce page will not ask you for your credit card number, but will ask your personal page to carry out a transaction its behalf.
You will have complete control over your personal URL framework page. But, you can maintain it in any way you see fit.