The results of numerous studies of the symmetry of the superconducting energy gap and the properties of the pseudogap in underdoped cuprate superconductors, performed in the last two decades, may provide the basis for the development of a consistent and generally accepted microscopic theory of high-Tc superconductivity. Superconducting magnets and applications in the power sector require the availability of industrially manufactured superconducting wires and tapes of high performance in piece lengths of more than one kilometer at a reasonable cost level. There is still a rapid progress in the development of RE-123 coated conductors. The performance of developmental iron-based superconductor wires and tapes suggests that these materials may become an alternative to RE-123 coated conductors, Bi-2212 wires and Bi-2223 tapes for the generation of very high magnetic fields at 4 K. High-Tc superconductivity is an enabling technology for the construction of compact fusion power plants operated at peak magnetic fields of more than 20 T at the magnet conductors. The large demand of high-Tc superconductors for fusion projects led to an upscale of the production capacity of RE-123 coated conductors and may also reduce the manufacturing cost to a level making them more attractive for power applications.