A method for providing additional information by an electrical apparatus, the method comprising: receiving first source data from a server and output the first source data to a terminal apparatus, wherein the terminal apparatus displays a content corresponding to the first source data received from the apparatus; extracting at least one keyword from the first source data; identifying a user viewing the content displayed in the terminal apparatus based on identification information stored in the electrical apparatus; detecting context information of the identified user; determining at least one keyword from among the extracted at least one keyword based on the detected context information; acquiring first additional information corresponding to the determined at least one keyword; and outputting the first additional information to the terminal apparatus, wherein the terminal apparatus displays the first additional information received from the apparatus, characterized in that the method further comprises: in response to a user's reaction to the first additional information displayed in the terminal apparatus, updating reaction history information of the context information based on the user's reaction, and in response to receiving second source data from the server, extracting at least one keyword from the second source data, determining at least one keyword from among the extracted at least one keyword based on the reaction history information, acquiring second additional information corresponding to the determined at least one keyword and outputting the second additional information to the terminal apparatus. receiving first source data from a server and output the first source data to a terminal apparatus, wherein the terminal apparatus displays a content corresponding to the first source data received from the apparatus; extracting at least one keyword from the first source data; identifying a user viewing the content displayed in the terminal apparatus based on identification information stored in the electrical apparatus; detecting context information of the identified user; determining at least one keyword from among the extracted at least one keyword based on the detected context information; acquiring first additional information corresponding to the determined at least one keyword; and outputting the first additional information to the terminal apparatus, wherein the terminal apparatus displays the first additional information received from the apparatus, characterized in that the method further comprises: in response to a user's reaction to the first additional information displayed in the terminal apparatus, updating reaction history information of the context information based on the user's reaction, and in response to receiving second source data from the server, extracting at least one keyword from the second source data, determining at least one keyword from among the extracted at least one keyword based on the reaction history information, acquiring second additional information corresponding to the determined at least one keyword and outputting the second additional information to the terminal apparatus. in response to a user's reaction to the first additional information displayed in the terminal apparatus, updating reaction history information of the context information based on the user's reaction, and in response to receiving second source data from the server, extracting at least one keyword from the second source data, determining at least one keyword from among the extracted at least one keyword based on the reaction history information, acquiring second additional information corresponding to the determined at least one keyword and outputting the second additional information to the terminal apparatus.