Wow! Why didn't I have one of these when I was a kid? It clips securely onto the neck of your guitar (or various other instruments - mine's an old guitar), then you pluck any string and it shows clearly the note and which string number this note should be, and how far off it is from the right pitch. That sounds complicated but it's easy! Just tighten or loosen in the direction indicated and when it flashes green, there you go - tuned. Takes seconds. And it's a metronome too... what a marvellous little thing this is!