Spectroscopic Parallax is the determination of the distance to a star through Spectrography. Like Parallax, it offers a means to determine the distance to a star, but the word "parallax" is otherwise unrelated and misleading regarding the method, which is as follows: from a star's spectrum, its Spectral Class can be determined, and its Absolute Magnitude can be estimated. The distance is derived by comparing this to its Apparent Magnitude.
It yields an estimate but there are factors that confound the result: Reddening and the differences in absolute Magnitude due to stellar factors other than spectral class: age, rotation, composition at time of Star Formation, companions, etc.
Luminosity Distance (dL)
Main Sequence Fitting
Stellar Distance Determination