The talk will be based on work done by Furstenberg, taken mainly from his paper "Randon Walks and Discrete Subgroups of Lie Groups". We will present the idea of a boundary attached to a random walk on a group, and explain intuitively how it can be applied to prove that SL2(R) and SLn(R) - for n greater than 2 - do not have isomorphic lattices. Then we focus on a key step in that proof: Constructing a random walk on a lattice in SLn(R) that has the same boundary as a "spherical" random walk on SLn(R) itself.