What's the difference between "obrigada" & "obrigado" please?

Question

Answer

If you are a woman then you must say "obrigada" and if you are a man you must say "obrigado".

Answer

Obrigado for boy and men
Obrigada for girl and woman

Answer

If you are a girl you have to say: obrigadA , if you are a boy, you have to say obrigadO.

Answer

Obrigado is used by men.
Obrigada is used by women.
And women also say obrigado more frequently than obrigada.

Answer

"Obrigado" we use for men, and "Obrigada" we use for woman.