  Recent experimental and theoretical developments in high-temperature
superconductivity are reviewed, and the empirically asymmetric behavior between
hole-doped and electron-doped cuprates is contrasted. A number of phenomena
previously considered as essential for the formation of cuprate
superconductivity, such as the pairing symmetry, pseudogap phenomenon, gapped
incommensurate spin fluctuations and charged stripes, are found to be
non-universal, and are likely the consequence of competing orders. It is
suggested that the only ubiquitous properties among all cuprates are the strong
electronic correlation and antiferromagnetic spin interaction in the CuO2
planes.
