The AM1808 SoC has 1 USB 2.0 On-The-Go Port (OTG).
This is the port that you connect to your computer.
Although the SoC supports OTG, it is not usable on the EV3. The OTG spec requires a Micro A/B connector and there are some missing jumpers on the EV3 circuit board.
It is possible to use the port in host mode instead of peripheral mode, though, if you supply your own 5V. See Issue #230 for more information.
The OTG port does not support isochronous transfers. See Issue #230.