Phosphor converted white light emitting diodes (w-LEDs) are garnering increasing attention in solid state lighting for the next generation of illumination due to their merits, including longer life, greater efficiency, compactness, reliability, low power consumption, and environmental friendliness. The quality of w-LEDs used in lighting and displays is affected by phosphors. There has been much focus on the creation of a ground-breaking single phase white light emitting phosphor with high efficiency, chromatic stability, an optimum color rendering index, and low associated color temperature. This review includes an introduction to rare earth activated phosphors as well as the basic benefits of phosphors for w-LEDs. To achieve the desired color-tunable emission suited for w-LEDs, the energy transfer mechanism between sensitizer and activator doped with inorganic host phosphors it primarily considered. In this article, we also covere a recent study on the energy transfer mechanism between Eu2+, Mn2+, Tb3+, Sm3+, Ce3+, and Tb3+. It is also possible to briefly emphasize the impact of charge compensation and other substitutions, such as (i) cationic, (ii) anionic, and (iii) cationic-anionic substitutions, on the color-tunable emission.