We have tried to describe two aspects of MIMO channels: channel capacity and channel modeling. We have analyzed the channel capacity of static and fading MIMO channels when the channel side information is available both at the transmitter and receiver, and when it is available only at the receiver. We have then modeled the MIMO channel in physical and angular domains to understand how it provides spatial multiplexing with the help of degrees of freedom. In physical domain modeling, we have modeled the MIMO channel in terms of individual physical paths. In angular domain modeling, we have described the MIMO channel with respect to fixed spatial basis functions defined by fixed angles that are determined by the spatial resolution of the antenna arrays. All the simulations have been performed on MATLAB 7.4.0.287 (R2007a).