ARCHOS Fusion Storage has been developped by ARCHOS to allow you extend your internal storage with a micro-SD card.
Your internal storage is by default separated from your external memory and some applications can only be installed in your internal storage.
For example, if your device has a 8-GB internal storage and you activate ARCHOS Fusion Storage by inserting a 64-GB micro-SD card, the system will inform you that you have a total of 72 GB* to install apps and their related data.
To activate ARCHOS Fusion Storage, see the following Q/A.
* 1 GB = 1 billion bytes. If the card is formatted, the available storage is less.