Nit is a non-SI name also used for the luminance or brightness of an object that is reflecting or, like a TV display, emitting light. The SI unit is candela per square metre (cd/m2)
1 Nit = 1 cd/m2
So the term Nits or candelas per square metre are used interchangeably and frequently used to describe the brightness (luminance) of a TV display or cinema screen.
See also: HDR, Gamma, EOTF