server for controlling an external device, the server comprising: a communicator; a memory configured to store at least one natural language understanding, NLU, engine, which generates a command corresponding to a user's utterance; and a processor configured to: control the communicator to receive, from a pairing device paired to the external device, the user's utterance to control the external device and information about at least one external device registered with the pairing device; extract a portion of a call sign of the external device and a portion of an operation of the external device from the user's utterance; determine an NLU engine corresponding to the portion of the call sign of the external device, from among the at least one NLU engine, based on the user's utterance and the information about the at least one external device; transmit the information of the external device corresponding to the determined NLU engine and an NLU result to a command-generating engine; generate a natural language-generating result utterance and the command controlling the external device based on the user's utterance, using the determined NLU engine; determine whether the external device is paired to the pairing device via near-field communication, and: when the external device is determined to not be paired to the pairing device via near-field communication, control the communicator to transmit the NLG result utterance and an ID of the external device to the pairing device, and to transmit the generated command directly to the external device; when the external device is determined to be paired to the pairing device via near-field communication, control the communicator to transmit the NLG result utterance, the ID of the external device, and the generated command to the pairing device. a communicator; a memory configured to store at least one natural language understanding, NLU, engine, which generates a command corresponding to a user's utterance; and a processor configured to: control the communicator to receive, from a pairing device paired to the external device, the user's utterance to control the external device and information about at least one external device registered with the pairing device; extract a portion of a call sign of the external device and a portion of an operation of the external device from the user's utterance; determine an NLU engine corresponding to the portion of the call sign of the external device, from among the at least one NLU engine, based on the user's utterance and the information about the at least one external device; transmit the information of the external device corresponding to the determined NLU engine and an NLU result to a command-generating engine; generate a natural language-generating result utterance and the command controlling the external device based on the user's utterance, using the determined NLU engine; determine whether the external device is paired to the pairing device via near-field communication, and: when the external device is determined to not be paired to the pairing device via near-field communication, control the communicator to transmit the NLG result utterance and an ID of the external device to the pairing device, and to transmit the generated command directly to the external device; when the external device is determined to be paired to the pairing device via near-field communication, control the communicator to transmit the NLG result utterance, the ID of the external device, and the generated command to the pairing device. control the communicator to receive, from a pairing device paired to the external device, the user's utterance to control the external device and information about at least one external device registered with the pairing device; extract a portion of a call sign of the external device and a portion of an operation of the external device from the user's utterance; determine an NLU engine corresponding to the portion of the call sign of the external device, from among the at least one NLU engine, based on the user's utterance and the information about the at least one external device; transmit the information of the external device corresponding to the determined NLU engine and an NLU result to a command-generating engine; generate a natural language-generating result utterance and the command controlling the external device based on the user's utterance, using the determined NLU engine; determine whether the external device is paired to the pairing device via near-field communication, and: when the external device is determined to not be paired to the pairing device via near-field communication, control the communicator to transmit the NLG result utterance and an ID of the external device to the pairing device, and to transmit the generated command directly to the external device; when the external device is determined to be paired to the pairing device via near-field communication, control the communicator to transmit the NLG result utterance, the ID of the external device, and the generated command to the pairing device. when the external device is determined to not be paired to the pairing device via near-field communication, control the communicator to transmit the NLG result utterance and an ID of the external device to the pairing device, and to transmit the generated command directly to the external device; when the external device is determined to be paired to the pairing device via near-field communication, control the communicator to transmit the NLG result utterance, the ID of the external device, and the generated command to the pairing device.