RxSwift asObservable().subscribeと.asDriver().drive違い

reactive programming - What is the difference between .subscribe and .drive - Stack Overflow

xxx.rx.isOn.asObservable()
            .subscribe(onNext: { [weak self] bool in

xxx.rx.isOn.asObservable()
            .subscribe

を asObservable() なしで subscribe

xxx.rx.isOn.subscribe

するとtrue/false逆転したような？

BehaviorRelayは RxCocoaのもの？