1. New files structure There are 2 major changes in the Magento-2 file structure. I) Everything is placed directly under the app structure. II) Every module has its own VIEW directory in which you can access all template, layout, js, and css/less files of any specific module. This is no doubt a big help for module developers as they can have more opportunities for customization without changing core site functionality. 
There are 4 types of directories in Magento 2 Primary System Application Public – The Primary forlder cannot be changed. They include: base directory, code directory /app/code, lib directory /lib. – The System forlder include: DI directory /var/di, generation directory /var/generation, etc directory /app/etc.To change the location of the system directory, you need to run EntryPoint class: – The Application directories include: design directory /app/design, app directory /app/code, var directory /var, temporary directory /var/tmp, cache directory /var/cache), log directory /var/log and session directory /var/session. – The Public directories include: pub directory /pub, pub_lib directory /pub/lib, media directory /pub/media, upload directory /pub/upload, static directory /pub/static, pub_view_cache directory /pub/cache.
There are 4 types of directories in Magento 2 Primary System Application Public – The Primary forlder cannot be changed. They include: base directory, code directory /app/code, lib directory /lib. – The System forlder include: DI directory /var/di, generation directory /var/generation, etc directory /app/etc.To change the location of the system directory, you need to run EntryPoint class: – The Application directories include: design directory /app/design, app directory /app/code, var directory /var, temporary directory /var/tmp, cache directory /var/cache), log directory /var/log and session directory /var/session. – The Public directories include: pub directory /pub, pub_lib directory /pub/lib, media directory /pub/media, upload directory /pub/upload, static directory /pub/static, pub_view_cache directory /pub/cache.