USB 3 has extra pins. On the main rectangular plug, they just crammed the extra pins in there. But the micro plug was too small to do that. So, to keep it compatible with USB 2 as well, they basically made it two plugs in one. USB 3 allows for higher voltages and faster connections.
There’s also a Type C out there now that added a Video-out port into the mix, and is reversible, meaning you can plug it into the wall to charge or plug in a USB device.
Here you go. Not really all that micro anymore. That’s the one that was on my hard drive I got for my birthday.
