I am new to Magento 2...and trying to learn CODEPOOL in Magento 2. This is a very basic question regarding Magento 2 Folder Structure.Magento 2 is differ from other previous version like Magento 1.9.1,1.9.0 ...
Magento 2 is significantly different from Magento 1.X and s not backward compatible as well.
In Magento 2,
app/code/[Company]/[Module]
[MAGE_ROOT]/vendor/magento/
. for example Catalog Module is now at [MAGE_ROOT]/vendor/magento/module-catalog
having the module name Magento_Catalog
[MAGE_ROOT]/vendor/magento/theme-frontend-luma
or [MAGE_ROOT]/vendor/magento/theme-adminhtml-backend
Some Used Technologies
Good Tutorials to Follow
Give it a try. It's complex, more advanced. But worth learning...