In this master’s theses I will take a look at the interesting world of auctions. The first part of my theses will take a look at the auction theory in general and will introduce the principles and the basic concepts. I will be explaining the common terms that are used in the related literature in a deeper way and focus also to the facts behind them. In the second part, I will focus on the classical paper by Riley and Samuelson (1981) called Optimal Auctions, where they e.g. show how the theory of revenue indifference can be proven when certain assumptions hold. This paper can be considered important to the economic theory in general and proves a claim made by William Vicrey in the early 1960’s that auctions, which seems to be very differen...