Please tell me the difference between these two items.

My nephew plays the violin in a symphony orchestra.

Gojūonchū, ka sa ta ha no shigyō ni, nigoreru on ari. Seion moji no kata ni, ゛ ten o fushite, sono shirushi to seri.Among the fifty sounds, those of the ka, sa, ta and ha-rows can be muddied up. They are written by attaching the dots ゛ on the shoulders of the letters for the clear sounds.