MageForge

Learn the structure by ownership, not by memorizing names

If folder names feel hard to memorize, do not start with a list. Start with a simple question:

Who owns this part of Magento, and what is it used for?

You own it: app/code, app/design, app/i18n, and usually app/etc/config.php.
The environment owns it: app/etc/env.php because it contains machine-specific and sensitive values.
Composer owns it: vendor/. You install it, but you do not hand-edit it.
Magento generates it: generated/ and parts of pub/static.
Runtime owns it: var/ for logs, cache, reports, and temporary files.
The browser should see it: pub/.

Imagine Magento as a building:

pub/ is the front door customers are allowed to enter.
app/code is your workshop where you build custom functionality.
vendor/ is equipment delivered from suppliers; if you modify it directly, the next delivery can replace it.
generated/ is machine-produced helper material.
var/ is the storage room for temporary operational stuff.
app/design is how the building looks.

When you see an exam question, ask yourself:

Is this custom code, shared config, generated code, public output, or temporary runtime data?
Should I edit it by hand, or should a tool own it?
Should it be public, private, versioned, or disposable?

That reasoning will usually eliminate the wrong answers quickly.

Question: "Where should a third-party extension live?"

Reasoning: Third-party code should be managed by Composer, so the safe answer is vendor/, not app/code.

Question: "Which file should not be committed because it is environment-specific?"

Reasoning: Secrets and machine-specific services belong in app/etc/env.php.

Question: "Why should the web server point to pub/?"

Reasoning: It reduces exposure of sensitive folders and keeps the public entry point narrow.

bash

1bin/magento cache:flush
2bin/magento module:enable Vendor_Module
3bin/magento setup:upgrade
4bin/magento setup:static-content:deploy