Frames contain other widgets. Buttons cause a specific action. Labels display short texts. Text objects provide text browsers and editors. Scroll bars let the user scroll through large list boxes, large texts, etc.
Canvases permit almost arbitrary graphics displays.
Menu buttons and menus create pop-up menus. There are also various image objects to display drawings, photos, etc. For more information about these widgets, see the Tkinter documentation and the Tk man pages. Instead of typing the filename, a file browser can be used. It also defines the two full-window widgets by classes, one for the text display window, and one for the main window.