There are a few features I can highlight. If you play around with it, you can see that clicking on the fretboard will show the note. You can also show the intervals and color the notes the way I like to color my fretboard diagrams (Orange: root, blue: third, green: fifth, purple: seventh). You can change the key, and if you go down to the tabbed 'Dictionary' on the left, you can repaint the notes per an arpeggio or scale.
You can also drag these 'Notegroups' over to the 'Player/Dashboard' on the right. This lets you cycle through the scales or arps in a 2-5-1 for instance and see how the notes change. These Notegroup buttons only repaint notes you have painted. The gray bars below the fretboard can paint entire frets quickly.
If you want to make a "Quiz" for yourself, you can enter a Page Title and then paint all the notes that are 'correct.' When you click 'Quiz Link,' you will get a blank fretboard for you to fill in all the notes satisfying the page title (e.g., Major Scale), and then click the "Check Answer!" button to see correct notes in green and wrong notes in red.
You can also use the 'Link' link to generate a URL which will reproduce all the notes and settings you've chosen. There are examples of these at the bottom.
Finally, there is a 'Random Interval' button which creates a random interval quiz. The red note would be the root note and the green note would be its 'interval.'
Enjoy! I'll be trying to update some things in the future. I really like seeing how the notes appear in a position through a series of changes. Also, quizzing myself on the intervals is something I need to do every day.