The main effects of atmospheric turbulence on the laser beams propagation are scintillation, beam wandering, and phase front distortion. The first two can be compensated simply by using aperture averaging, whereas the later, which is of high importance in high data rates free space optics communications, is much more complex. This paper gives a review of principal analytical methods used to simulate and characterize the optical beam propagation through the turbulence channel focussing on phase front distortion. The paper presents simple models suitable for computer simulations of beam wandering and scintillation. This is followed by more complex theoretical approaches in analysing the turbulence induced phase front distortion and the calculation of the mutual coherence function of partially coherent beams propagating through an inhomogeneous medium. The theoretical analysis of beam coherence and phase front distortion due to turbulence represents the first step for elaboration of the mitigation methods.