Nu-Disco emerged primarily in the mid-to-late 2000s as a contemporary, mostly electronic interpretation of disco music. It has origins as far back as the mid-1990s, however, when a small number of labels released dubby, repetitive disco re-edits, and when house artists began incorporating overt disco samples & styles for a more retro sound.
Most nu-disco has no named sub-style or clearly defining characteristics, other than being rhythmically disco-based and not fitting into any other genre.
Nu-Disco often makes use of the standard disco rhythm (kick drum on every beat and a closed hi-hat on every eighth note), rather than the "high-energy" disco rhythm which underpins much house music (same kick but with an open hi-hat on the "off beat", i.e. every eighth note in between). It may also incorporate 1980s Italo Disco-style synths & drum machines.
Sometimes re-edits (often with added effects) of original-era disco & boogie tracks are referred to as nu-disco. Some nu-disco is in a slowed-down "slow motion"/"cosmic" style. Some is quite fast and "hard" and can be more precisely described as "electro-disco" or "electro-house" depending on its resemblance to electro, electroclash, disco, and house. Some nu-disco has a very retro, Italo-Disco inspired sound but probably should not be tagged as Italo-Disco. Some is synthy and uplifting in-a-style of pop music.
However, Nu-Disco should not be confused with other more specific styles also inspired by disco, such as French House or Disco House, which differ from Nu-Disco by having a repetitive 4/4 structure, typical for house music, also most often based on disco samples.