Analysis of the strong emission-line data of 281 QSOs shows that these are consistent with the following hypotheses : (1) There is no redshift, (2) The strength of the emission lines is due to laser action, and (3) The composition of the emission region of QSOs is approximately the same as that of normal stellar atmospheres. A search was made for common lines in QSOs and in laboratory observed laser lines in such atoms and ions, which have high abundance in stellar atmospherea. Twenty-four such wavelengths were found. A realistic model of the QSOs, based on these hypotheses is proposed. A QSO is a star with a rapidly expanding atmosphere, in which population inversion is occurring. This atmosphere can be approximated by a decaying plasma. Properties of such a plasma are reviewed. A given transition in an atom can undergo laser action only within narrow ranges of the electron density (ne), electron temperature (Te) and the density of the ground state atoms n(1). ne, Te, n(1) plot is introduced to classify the QSOs. Consequences of the proposed model are discussed, taking the group consisting of 3C 191, PHL 938, PKS 0119-04 and BO 6 as an example. Other similar groups are pointed out (e.g., RS 23, PHL 1222, and 1548+115b). Intensity variations of the same line in different QSOs, and also in the same QSO, are shown to follow naturally from this model. Quantization in the redshift distribution is explained. Absorption spectra of QSOs are also discussed.