What are boy scouts?

And why does there have to be boy scouts and girls scouts instead of just scouts?

Is it like sports teams or something? If not, I don't think they should be divided.
Update: If it's just about having fun and adventure and it isn't about competition, why should it be divided?
Update 2: I heard that girl scouts is only about selling cookies. Is that true? Or do they have the fun activities boy scouts do as well?
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