What is documentation and what is it eaten with (how is it right, how is it better?)?

Question

Programming

What is documentation and why is it needed? How to write? What are the styles? (I really ask for examples, please)
Sending to Google is not the best option. I did this, but there is a lot of water when searching.
So I decided to take advantage of the question, since there is such an opportunity.

Answer 1

Take phpstorm, write a function/method. The main thing is to specify what the function accepts and returns.
If possible, use type hinting (explicit indication of the types of arguments and return value).
alt+enter on function name -> generate doc block - phpstorm generated doc blocks for you.
It remains to add a description to the function above and to the parameters to the right of them.