The Voigt profile is a model shape of spectral lines, i.e., a model line profile. It is the shape the Voigt function is a convolution of two distribution functions, that model the result of two types of line broadening together, Doppler broadening and pressure broadening. (These, and the result, are termed line broadening functions, or broadening functions, or BFs.) The math offers a means of analyzing a line regarding the two effects.
Voigt-function approximations have been developed since such convolutions are a computational challenge. With today's computing power, the approximations still may be useful for cases where such a model's calculation must be done many times, or for back-of-the-envelope estimates.