In this thesis, we will first introduce gravitational lensing, gravitational microlensing as a kind of gravitational lensing and describe its applications. In the first chapter of this thesis, we focus on the amplify of source’s light in gravitational microlensing. We then obtain the coefficient of light amplification over time and plot the diagram of a light curve for a source. At the end of the first chapter, we investigate the states that divert the microlensing light curve from its standard state and investigate how it helps for determining the physical parameters of the lens and source. In Chapter 2, we will explain another non-standard light curves that help us identify the phenomena of gravitational microlensing under different conditions. In Chapter 3, we will consider polarization in gravitational microlensing, which will help us to obtain the polarization of the star’s surface from the resulting images.