Homo Sapiens Use 10% Of Their Brain?

Hello,

I'd be glad if someone can help with this puzzling question.

Just took to studying again and the line I read that humans use 10% their brains throughout their life time. Why?

My question are, "What is the 90% left for?

And, why do we use the 10%?


But nobody knows,


There has to be a perfect and suitable explanation for this.