I'm running Android Things on a Raspberry Pi 3 Model B. I want to read NFC Tags, is it possible to do this? I've got like zero hardware knowledge about this stuff. All I know is how to write the necessary code.
A Raspberry Pi (or the other Dev kit) does not have NFC hardware. If you want to read NFC tags you need to get some hardware.
In addition to that, there is not user space driver for NFC, so you'd need to read it using a driver.
I only know of 2 chips that are sort of supported, both drivers are very limited. In fact, the simplest way to get them to work is to plug then into an Arduino and then communicate with the Arduino either using UART or I2C.
The best supported chip is RC-522. It reads mifare, but not sure how many other formats. You have a driver ported from arduino here: http://github.com/Galarzaa90/android-things-rc522 One of the important limitations is that it does not support card emulation.