In Twistronics we study the effect of relative twist between the layers of a material on the electronic properties of that layered materials. There are expected to be hundreds of layered materials which can give rise to thousands or even more layered materials with combination of layers and relative twist between the layers. There is a great possibility to encounter many exotic electronic properties in these rather less explored layered materials with relative twist between the layers. There is a lot to explore and understand, to unlock full potential of twistronics. A lot of theoretical and experimental studies have been done and are being done to explore the electronic properties of twisted bilayer graphene, making it a good material to start with to explore the hidden potential of twistronics. Here we present a simple theoretical model study for commensurate twisted bilayer graphene. Starting from understanding of moire pattern in twisted bilayer graphene our study goes through writing of tight binding Hamiltonian, computational codes to determine various model parameters, solution of Hamiltonian to obtain quasi particle energies and density of states near Fermi energy in twisted bilayer graphene. Our theoretical calculations have produced flat band near Dirac point and Van-Hove singularities near Fermi energy, which agree qualitatively with recent experimental studies.