An Emacs frame may or may not have a specified title. The frame title, if specified, appears in window decorations and icons as the name of the frame. If an Emacs frame has no specified title, the default title has the form ‘invocation-name@machine’ (if there is only one frame) or the selected window's buffer name (if there is more than one frame).
You can specify a title for the initial Emacs frame with a command line option:
The ‘--name’ option (see Resources) also specifies the title for the initial Emacs frame.