When the Pi Zero came out, one of the downsides (!) of the low-cost design was swapping the 'standard' USB A-port for a micro-B port. Now you have to use an 'OTG' cable instead of just plugging in a device.

There was also the matter of, if you didn't have anything connected to USB, and powered up the Pi Zero with an old Raspbian image, you'd get a strange warning

WARN::dwc_otg_handle_mode_mismatch_intr:68: Mode Mismatch Interrupt: currently in Device mode

Basically, the Pi sorta-trying to become a usb device rather than a usb host

Some awesome people on github sorted out that if you used the DWC2 USB driver, and patched a few files, you could get the Pi to act like a USB device (in linux-land this is called the USB Gadget system)

Thx for the tips from Andrew, as of May 2016, Raspbian Jessie does not require a new kernel

This tutorial is basically just a writeup of how you can follow along and turn your Pi zero into a USB Serial device or Ethernet device. That's two whole ways of being able to connect to your Pi zero just by plugging in a micro B cable! You don't even need to power your Pi seperately, as power is provided from your computer.