How does the script for automating any actions with the site work?

Question

Python

Hey!
I've been thinking about something like this. How do scripts work that allow you to automate certain actions on sites?
Let's say sites that, on behalf of a VK user, put likes and add random users as friends, or mass following on Instagram, or even just spam bots for regular sites on the web.
I believe that this can and should be done through the API (although I still have little idea what it is and how it works), but neither VK nor Instagram will ever provide their API to cheat services, and they work successfully for themselves.
Since I just started learning programming, it’s completely incomprehensible how it all happens, but it became very interesting.

Answer 1

They use libraries like Selenium that emulate a browser.

Answer 2

With the help of the API, you can, of course, engage in cheating. But not to long.
Cheat services use thousands of accounts in their dirty deeds. Some are banned, others appear.