A router is a piece of software that orchestrates the behavior of your user interface when the URL address changes. This accounts both for websites and native apps. Whenever you enter a certain part of the whole web/app structure or interact with it to go somewhere else, the URL changes. However, do you really want to load the new page entirely every time the URL changes? I doubt that.
The solution is called React Router. When you look at its code, it kind of looks like it is supposed to run a nuclear plant, not an Electron based app. Additionally, the API changes every half year or so without much support for the previous versions. Imagine that you're building your app with one router and then you have to change it every time the router changes. Simply put, we couldn't take that risk. Instead of using a complicated library full of hacks with over 10 000 lines, we wrote our own with 200 lines.
We've built a truly universal React Router for web, and Electron or nw.js apps that we continuously support. The main difference to standard routers is that it can change only particular components based on the data you pull. Last but not least, when you plug it into React, it just works. However, please bare in mind that the API interface is not finalized yet and will probably change until it reaches the 1.0 version.
While you're at it, tell us what you think. We'll be happy for your feedback.