The present disclosure describes a communication system that includes communication circuitry and processing circuitry. The processing circuitry is configured to collect a piece of user information of a user via the communication circuitry, analyze the collected piece of user information to obtain a user preference of the user, and identify a piece of advertisement as targeting the user according to the user preference. The processing circuitry is further configured to generate a guidance message based on reason of promotion information stored in association with the piece of advertisement, transmit the guidance message to a client terminal of the user, and transmit the piece of advertisement to the client terminal. The guidance message and the piece of advertisement are to be output as vocalized speeches of a voice agent of the client terminal.