The general picture (essence) of the tester?

Question

Books

There is no general picture (scheme) about testing, what is this work and where should you start studying this area (literature, webinars, courses)?

Answer 1

What a question, such an answer:
Press buttons and write/fill test cases at the exit.
There are many types of testing:
automatic, manual;
functional, interaction, security;
load, stress, etc.
Not to mention what technologies will be involved and what applications will be tested. The simplest option is to press buttons on test cases in the application's GUI, recording the output. It is more difficult to write large scripts in bash\python for example for complex scenarios.
Decide on the technologies in which you plan to engage in testing and study them.

Answer 2

The version of the work of testers is given in one of the comments: https://toster.ru/answer?answer_id=882374#answers_...