Your device has internal Memory of 16MB and External memory through Micro SD (up to 32G). This can be Internal Storage issue. You can delete text messages/emails/pictures which may take lot of space (internal memory). I would suggest you to transfer pictures to your Micro SD card to free Internal Storage.
MicroSD is a kind of removable flash memory card used for storing information. SD is an abbreviation of Secure Digital. The cards are used in cellular phones. They are also used in newer types of handheld GPS devices. You cannot add any Internal Storage (memory) to the device. You can save lot of device memory space by transferring your info to Micro SD card.