Please note: the Fretboard Visualizer plugin has been replaced by Fretboard Videos. Nevertheless, it is still available, in case you want to use it with a DAW. If you don't know what a DAW is, you don't need the plugin, use the videos!
The Visualizer is a plug-in, not a stand-alone application.
It is a 32-bit VSTi plugin, that still works with many 64-bit DAWs, but will not be upgraded anymore.
The Midi Fretboard visualizer can be used as a plugin in all (Windows) VSTi compatible programs (e.g. Cubase, Logic, Cakewalk/Sonar, Reaper, etc), and can be used to visualize the guitar midi files in the jazz exercises package in real time, while they are playing. In combination with the mp3 files, you can hear the recorded sound simultaneously, while watching the fretboard.
So even if you don't read music or TABS, this will show you everything in detail.
You need a Windows PC and a VSTi compatible host application: practically all decent computer recording applications support VSTi plugins. There are some very cheap VSTi hosts if you don't have one already (instruction video here). Reaper is a good one that you can try for free, for an unlimited time.
Unfortunately the plugin is not available for MacOS.
In the pdf guide that comes with the Jazz Exercises package, chapter 8 describes the visualizer installation in Cubase, which is similar to other VSTi hosts.
Reaper offers a unlimited-time tryout version with full functionality. If you are serious about practicing and improving your sound, you should anyway consider recording yourself: programs like Reaper provide everything you need for recording, except the physical recording interface, but, easy-to-use USB audio interfaces are quite cheap nowadays, so you you can record yourself in high quality at low cost. Listening back to your own recording is a very good way of finding out what's good and not yet so good in your playing. When you are not concentrating on playing, but just listening, you can really hear how your solo sounds. It can be a tough confrontation at first, but a great way to honestly assess your own performance. When it sounds good, it is very gratifying as well, and you'll want to do more!
Why a plugin, in stead of stand-alone application? Making a plugin takes a lot less programming effort (thus a less expensive product) than writing a complete program for playing midi and audio, while at the same time midi/audio players are already available in abundance, some at very low cost, and even for free, which support standard VSTi plugin formats. Secondly, getting a recording application is very good to record your own playing. Listening to your own playing is one of the best (and confronting!) ways of finding out what needs to be improved.
How does it really work?
The plugin uses midi information (notes) to display positions on a virtual fretboard. For this, it uses a midi track of the corresponding lesson. At the same time, an audio track (mp3), provides the real sound that goes with it. Optionally, you can also let the midi track itself generate sound. To do that you need to load another VSTi module that acts like a virtual instrument, such as a guitar, piano, or whatever you have available. The advantage of this is that you can play it at arbitrary speed, as fast or as slow as you want!
The schematic below shows how audio and midi track run in parallel to produce both sound and visual, running in sync.