Where is the modules folder in Opencart?

Question

opencart

Hello.
Where is the modules folder in Opencart?
We are talking about non-standard modules (those that download and connect).
Version 2.3.0.2

Answer 1

Fundamentally". The Catalog folder and the Catalog itself are essentially the same Module:

And for third-party packages, there is also a vendor folder:

Here is a typical structure of such a module: