A control method of an electronic device includes receiving a user voice; based on a user command corresponding to the user voice being already registered, providing at least one audio or visual indication that the user command is unable to be registered as a voice command; based on the user command corresponding to the user voice not being registered yet, providing at least one audio or visual indication that the user command is able to be registered as a voice command; and based on the user command corresponding to the user voice being related to a prohibited expression, providing at least one audio or visual indication that the user command is related to the prohibited expression.