A superluminous supernova (SLSN or superluminous SN or hypernova) is a stellar explosion more energetic than a normal supernova, i.e., they can be classified as very large supernovae, basically if they are an order-of-magnitude more energetic (on the order of ten foe or greater). Most are Type Ic or Type IIn supernovae, termed Type I SLSN (or SLSN-I), Type II SLSN (or SLSN-II), They are theorized to be core collapse supernovae, but some don't fit that pattern. They are also thought to be the origin of long gamma-ray bursts (LGRBs).
A third type called SLSN-R (for "radioactive") apparently with electromagnetic radiation produced by a radioactive nickel isotope.
Among theories explaining their mechanisms:
It is thought that early O-type stars generally produce SLSNs.
The favored terminology is likely to evolve, e.g., more specific names for some these mechanisms and consensus may well give the terms hypernova and superluminous supernova more specific meanings.