Proteins are molecular machines which play a vital role in life. The study of proteins has proved to be a daunting problem because of its sheer complexity. We discuss how two physics-based ideas, spin glasses and the phase behavior of a compact flexible tube, are useful for the development of a framework for understanding proteins. The tube picture provides a simple explanation for how geometry and symmetry determine the menu of possible native state folds of proteins, whereas the spin glass paradigm is useful for determining how one of the folds from this predetermined menu is selected as the native-state structure of a given protein sequence.