Understanding music flats and sharps

Okay, so you know that there are really 7 natural notes:
A B C D E F G

On a guitar, if you play the 5 string (the 2nd string from the top), 3rd fret, you get a C note. If you play the fourth fret, you get a C sharp which is also known as a D flat. The 5th fret would give you a D. Therefore, the 6th fret is a? Yes, D sharp aka E flat. Get my drift? There is no B sharp, that's the only thing you need to know.

Check out the image below

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