Whats consists of a weapons squad and a weapons platoon?

I know that a rifle squad is made of 2 fire teams and a leader and a rifle platoon is made of 2 rifle squads and a weapons squad{what is that?) and that an infantry company is made of 3 rifle platoons and 1 weapons platoon {now what is THAT) can someone please explain these to me and correct me if im wrong, btw im talking about the U.S Army.