In this two part series I will be developing the Feynman’s path integral formulation of Quantum Mechanics. In this part one of the lecture, I will talk about where does the whole idea of infinite or all the possible path comes from, where I will use the double slit experiment and will describe the amplitudes of the particles propagation to its desired destination, then we will try to generalize the result which is where the whole idea of infinite paths would pop up!