Why is a cookie notice shown on websites?

Question

Law in IT

Previously, only on foreign sites I saw this and now they do it on ours too.
Usually the message is pinned at the bottom and looks like this:

We use a variety of tools, including cookies, to provide the core services and features of our site, and to collect data about how visitors interact with our site, products and services. By clicking "Accept", you agree to our use of such tools for advertising, analytics and support.

why is this? and what happens if it is not done?

Answer 1

Why do we need cookie warnings?
Do I need notification about the use of cookies?
Why do sites warn about the use of cookies?
Why do many sites have a notification about the use of cookies?
Do Russian sites need to notify about the use of cookies?
Are there cookie warning requirements?