You can find two different memories in the SBC:
External flash memory, 16MB capacity
MicroSD memory, up to 32GB capacity
If the SBC has a microSD card inserted it will use it as its main memory.
If no microSD card is inserted, the SBC will use its external flash memory as its main memory.
When connecting the SBC to a computer via USB, the main memory is always shown as an external drive.
For examples about how to use the external flash or microSD memory, check the Basic examples section.