Abstract: Nelson's model describes the system of an electrically charged quantum particle coupled to a Bose field. Under an infrared (IR) cutoff condition it can be shown that the system has a unique ground state. I will present a rigorous derivation of the properties of this ground state (such as boson distribution, average field and fluctuations, exponential localization of the particle). Also, I will show that in 3D the model is IR singular while for higher dimensions it is IR regular, and that by removing the infrared cutoff the physical picture remains unchanged.