Tkinter is the standard GUI (Graphical User Interface) toolkit for Python. It provides a simple way to create windows, dialogs, buttons, labels, and other GUI widgets. Tkinter is a wrapper around Tcl/Tk, a robust toolkit for creating graphical user interfaces. Being part of the standard Python library, it's widely available and does not require any external dependencies. Tkinter is known for its simplicity and ease of use, making it an ideal choice for beginners and for rapid development of small to medium-sized desktop applications. Despite its simplicity, Tkinter is quite powerful and can be used to create complex user interfaces.