A Frame.htmlframe is just an invisible container into which we can pack other widgets, grouping them together. The use of frames is in packing: the grouping is necessary most of the time to achieve the desired layout with the standard packer.
Moreover, when using a frame, we can use a different packer (see Sect. 2.6) than in the parent widget; for example, we can use the grid packer inside a window using the standard packer.