In this thesis, we study some properties of MDS codes and we mainly focus on the MDS codes conjecture. In the first chapter we define MDS codes, show some examples and basic properties of MDS codes, for example a link between MDS codes and Latin squares or rectangles. Afterwards we state the MDS codes conjecture and prove it in several cases. In the third chapter we can observe the relationship between MDS codes and narcs in projective geometries. Finally we present those known cases, for which the MDS conjecture holds.