Graphitic carbon nitride (g-C₃N₄) has become an important material because of its attractive optoelectronic properties. It has been applied in various fields such as photovoltaics, biosensing, and photocatalysis. As an analog of graphene, it has layers which can be transformed into different morphologies including nanosheets, nanotubes, and quantum dots. Pristine g-C₃N₄ exhibits a low specific surface area and a high rate of recombination of photogenerated charges. Therefore, modification is required in order to improve its properties, for instance, by doping it with other atoms and transforming it into another morphology. In this review, the synthesis, modifications, and applications of g-C₃N₄ are evaluated. The use of theoretical strategies to understand various properties of g-C₃N₄ and its composites is highlighted. Moreover, the current status on the application of g-C₃N₄ is explored. Ultimately, this review will shed more light on the uses and modifications of g-C₃N₄ for future applications.