The new 8.1 version of the Windows Phone OS introduced several functionalities: the personal voice-assistant Cortana, the notification center, a new calendar, a word flow keyboard, the complete phone backup, the projection of the smartphone screen on a PC (using a wireless or an USB connection) and, last but not least, the capability to decide where to install new apps/music/photos/downloads … and possibly change your mind even later.
New Lumia models very often have the capability to extend the smartphone memory with an external SD card and so it is very useful to decide where to store new apps or data (i.e. in the internal phone memory or in the external SD) in order to not completely fill the phone internal storage: moreover, it is now very easy also to move each app from one storage to the other one.
As you can see from the following screenshots, all these features can be reached going to Settings->Storage sense (Impostazioni->Sensore memoria): then you can set the default storage for each kind of data/app.
If you want to move some already installed apps from the phone memory to the SD, after clicking on the phone (telefono) text, you go to a detail page where you can see the list of all the installed apps: here, clicking on one app, you can go to a page where you can choose to move it on the SD card. Note that not all the apps can be moved to the external SD (e.g. Whatsapp) because this is not allowed by the publisher: for some intensive apps, like graphics intensive games, the performance may decrease a bit when they’re put in SD (e.g. you could hear small cuttings and lagging in background music), but this depends a lot also on your phone’s processor and your SD Card’s class.
PS: in the previous screenshot, the option move to SD is disabled only because the Lumia 920 have not an SD slot!
If the language is italian, here you can find the relevant pages: