Pseudorandomness of Kloosterman and Salie Sums

We present some old and more recent results which suggest that Kloosterman and Salie sums have a pseudorandom behaviour which is traditionally attributedto the Mobius function. In particular, we describe several results about the non-correlation of Kloosterman and Salie sums between themselves and also with some classical number theoretic functions such as the Mobius function and the sums of binary digits. Arithmetic applications of these results will be outlined as well. We will also formulate some analogues of the Chowla Conjecture for Kloosterman and Salie Sums and discuss sone possible approaches to establishing it "on average".