What are option resource and class names?
Every Tk widget option has three names: the option name, the resource name, and the class name. The option name begins with a hyphen and is all lowercase; it’s used when creating widgets, and with the configure and cget commands. The resource and class names are used to initialize option default values by querying the option database. The resource name is usually just the option name minus the hyphen, but may contain uppercase letters at word boundaries; the class name is usually just the resource name with an initial capital, but not always.
