You have stumbled upon a repository which contains files for the Nixie Tap device.
What is a Nixie Tap? It's an ESP8266-based Nixie display in a nice enclosure.
By default, it's an internet-synchronized clock, but it could be whatever you desire: IFTTT button, cryptocurrency price ticker, temperature alarm...
To build the latest hardware, use the files from the hardware folder, buy the parts and PCBs, and fire up the soldering iron.
To build the latest firmware, open the 'firmware' repo in VS Code / Github Atom with PlatformIO, and download it to the ESP from there.
There is also a website with more details, here: https://mladendinic.com/nixietap/
Have a nice day!