1. A method of displaying a plurality of display windows on a screen by using a device, the method comprising: displaying a first display window of a first application on the screen; receiving a first user input that selects an object included in the first display window of the first application; displaying, on the first display window, a list of applications matching a window display mode of the first display window in response to the first user input, the window display mode being for displaying a window of an application according to at least one of a size, a displaying position or a displaying priority of the window; receiving a second user input that selects a second application included in the list of applications; displaying a second display window of the second application selected from the list of applications in the window display mode of the first display window; displaying the list of applications when a predetermined object included in the second display window is selected; and displaying a third display window, including the execution result of an application selected from the list of applications, the third display window being separate from the first display window, wherein the window display mode is set to an application, wherein each application of the list of applications renders a window having a window display mode that is same as the window display mode of the first display window, and wherein the second display window and third display window overlap each other.