This section of the course covers how to remotely control your Nano Mouse. If you do not have the hardware or the desire to complete this section, you can safely skip it and still learn everything you need to make your Nano Mouse solve a maze.
That said, learning to remote control your robot is a lot of fun. You can use the track pad of a Macintosh computer, or the accelerometer of an Android phone/tablet. If you would like to control your robot using any other device (e.g.: an iPhone or a Blackberry) you'll have to use a NodeMCU and follow the video tutorials I've created that outline how to code a web app that communicates via WiFi.
Personally, I prefer writing an Android specific app that uses Bluetooth. It tends to work a little more reliably. If you do not have an Android tablet or cell phone, I highly recommend purchasing one because writing your own Android apps is easy and free with App Inventor 2 (this is not the case with Apple products). Also, Android phones/tablets are equipped with various sensors that you can use to augment what you do with your Arduino (or any other microcontroller for that matter). Amazon's Kindle Fire is almost certainly the least expensive tablet you can purchase for this purpose and is what I use with my students. If you are an educator working with a classroom full of students, you can get away with just a few tablets as your students will likely reach this section at different times.
Prior to coding an Android app to remote control your robot, I recommend working through some beginner tutorials so that you understand what you're doing before you work through my video tutorials.