The search for new materials has aroused the increasing interest of researchers from different areas, especially if such materials enable the development of smaller and more efficient devices than others already on the market. Among the main types of materials sought are those that can be obtained in two-dimensional (2D) form, due to the successful discovery of graphene, which is a 2D material with excellent electronic and mechanical properties, for example. A class of materials that can be obtained in 2D form and that has gained prominence in recent times is that of Transition Metal Dichalcogenides (TMDs). Some of these materials are already well known and several works have used calculations of first principles through the Density Functional Theory (DFT) to obtain properties of two-dimensional TMDs. The possibility of predicting properties (electronic and vibrational, for example) and the structure of TMDs through computer simulations is extremely advantageous, as it makes a previous experimental study of such materials unnecessary. Thus, in this work, a study will be carried out on two-dimensional materials, especially on TMDs and their characteristics. In addition, the DFT will be studied in order to describe how such a theory was built and on its computational implementation, which is what makes it possible to perform computer simulations of multi-electronic systems. Finally, a representation of the gains from studying materials such as transition metal dichalcogenides through the density functional theory will be shown.