Single module applications have only one module. This application does not mandate a namespace. It has a structure as –

single/

app/

controllers/

models/

views/

public/

css/

img/

js/

Multi-module uses the same document root for all the modules. Each directory in apps has an MVC structure of its own. Module-specific settings are configured using Module.php present in each module. The structure is like –

multiple/

apps/

frontend/

controllers/

models/

views/

Module.php backend/

controllers/

models/

views/

Module.php public/

css/

img/

js/

BY Best Interview Question ON 03 Apr 2019