Knowing where each note sits on the tenor banjo neck is what lets you pick up tunes by ear, follow a session tune off the page, and find your way when someone calls the key. Tab only takes you so far.
What Note? covers the open strings (G D A E) and the first five frets — the open position, where almost every trad tune is played. A marker lands on a string and fret; tap the note on the keyboard. Press Hear it to train your ear as you go.
GDAE is the same tuning as the fiddle and mandolin (the banjo sits an octave lower), so the note map carries straight over to both.
Start with Naturals, move to Chromatic when you're quick, or pick Scale to practise one key, such as D, G or A major, the keys most session tunes are in.