What is the difference between #include and using std::?

Question

C++ / C#

Hello. I understand that my question will seem to experienced programmers (and experienced ones for me are everyone who knows more than me), but I'll ask anyway. I started learning C++ quite recently and I want not just to memorize the material, but to understand why everything is arranged this way, i.e. why you need to write #include, why using std::, etc. So here's the specific question: how does using differ from include, if both are C ++ libraries in which we are looking for the operation we need? Please answer like a schoolboy, since the question, as I understand it, is appropriate) I'm afraid that I will miss something and after that everything will not go as we would like. Thank you.

Answer 1

#include is where classes, variables, scopes, etc. will come from.
using std is scope.
If you don't include #include "vector"
You can't access std::vector;