''who''可以help me??

加(豆)號 is for 補充.

e.g.
The person is sure to win. But 邊個?? The person climbs the fastest.

When you want to make it clearer you write

= The person, who climbs the fastest, is sure to win.

有逗號是因為兩個逗號中間的字只是作補充作用，即未必須要，沒有逗號是因為該句子之間果個phrase有助你辨認你講緊果個人