I'm assuming its a 16GB device??
Some space is taken up by the OS so thats why you only get access to 14.5GB.
After this, your data will be shared throughout the handset. You can choose to save all pics/videos/music to memory card.
There is a pesky "Other" folder that holds hidden temp files however that likes to eat up GB's. No way as of yet to access it and delete, there are new storage tools, that have had varied results. Some report very well, in my case not so well.