Rational drug designing encompasses several theoretical methods and in silico approaches involving molecular modeling, docking etc. to study the behavior and the properties of molecular systems. Specifically, the techniques employed in the fields of computational chemistry, computational biology, nanotechnology, and material science vary in complexity, and theoretical observations depend on the system type and the system size being investigated. Molecular modeling involves both quantum and molecular mechanics (QM & MM). The fundamental concepts of molecular modelling with suitable examples are elaborated. The present chapter also highlights the sequential flow of in silico approaches used for the purpose of drug designing, giving a brief snapshot of the software used for this purpose. The advanced techniques and applications of computational methods used for new drug development are explained. Thus, this chapter provides an insight into the various dimensions of computer-aided drug design; its driving force, recent development, and future prospects.