A display apparatus comprising: a signal reception unit for receiving an image signal of content; a signal processing unit for processing the image signal received by the signal reception unit according to a preset image processing process; a display unit for displaying an image based on the image signal processed by the signal processing unit; a communication unit for communicating with a plurality of servers respectively providing a plurality of services related to the content; and a controller configured: to extract a keyword related to the content from the received image signal and to display the keyword on the image displayed on the display unit, to display a single service identifier corresponding to one of the plurality of services alongside the keyword on the image, wherein the single service identifier comprises an identifier of a service provider within a service category, to change the displayed service identifier to a different service identifier in response to a first user input received at a user input unit, wherein the first user input comprises either a first set of shift instructions or a second set of shift instructions; the controller being arranged, in response to the first set of shift instructions from the user input unit, to change the displayed single service identifier so as to display an identifier of a service provider in a different service category from that currently displayed, and is arranged, in response to the second set of shift instructions from the user input unit, to change the displayed single service identifier so as to display an identifier of another service provider in the same service category as that currently displayed, if a service identifier currently displayed is selected by a second user input, to transmit the keyword through the communication unit to the server which provides the service corresponding to the selected service identifier, and to be provided with a service related to the content based on the keyword, from the server which corresponds to the selected service identifier. a signal reception unit for receiving an image signal of content; a signal processing unit for processing the image signal received by the signal reception unit according to a preset image processing process; a display unit for displaying an image based on the image signal processed by the signal processing unit; a communication unit for communicating with a plurality of servers respectively providing a plurality of services related to the content; and a controller configured: to extract a keyword related to the content from the received image signal and to display the keyword on the image displayed on the display unit, to display a single service identifier corresponding to one of the plurality of services alongside the keyword on the image, wherein the single service identifier comprises an identifier of a service provider within a service category, to change the displayed service identifier to a different service identifier in response to a first user input received at a user input unit, wherein the first user input comprises either a first set of shift instructions or a second set of shift instructions; the controller being arranged, in response to the first set of shift instructions from the user input unit, to change the displayed single service identifier so as to display an identifier of a service provider in a different service category from that currently displayed, and is arranged, in response to the second set of shift instructions from the user input unit, to change the displayed single service identifier so as to display an identifier of another service provider in the same service category as that currently displayed, if a service identifier currently displayed is selected by a second user input, to transmit the keyword through the communication unit to the server which provides the service corresponding to the selected service identifier, and to be provided with a service related to the content based on the keyword, from the server which corresponds to the selected service identifier. to extract a keyword related to the content from the received image signal and to display the keyword on the image displayed on the display unit, to display a single service identifier corresponding to one of the plurality of services alongside the keyword on the image, wherein the single service identifier comprises an identifier of a service provider within a service category, to change the displayed service identifier to a different service identifier in response to a first user input received at a user input unit, wherein the first user input comprises either a first set of shift instructions or a second set of shift instructions; the controller being arranged, in response to the first set of shift instructions from the user input unit, to change the displayed single service identifier so as to display an identifier of a service provider in a different service category from that currently displayed, and is arranged, in response to the second set of shift instructions from the user input unit, to change the displayed single service identifier so as to display an identifier of another service provider in the same service category as that currently displayed, if a service identifier currently displayed is selected by a second user input, to transmit the keyword through the communication unit to the server which provides the service corresponding to the selected service identifier, and to be provided with a service related to the content based on the keyword, from the server which corresponds to the selected service identifier.