This talk will build on Luis's introduction to k-Schur functions from last week. We will examine affine Stanley symmetric functions and their relationship to the k-tableaux used to characterize k-Schur functions. Stanley symmetric functions are used to study the number of reduced decompositions of words in the symmetric group; it turns out these are related to Schubert polynomial, which are used in the study of flag varieties. After a brief introduction to classical Stanley symmetric functions, we will get into affine Stanley symmetric functions, an analogue/generalization for the affine symmetric group.