The main objective of this bachelor's thesis will be to present the concept of quasirandomness in various mathematical contexts while proving all the pertinent results. We will introduce the results of Fan Chung and Ronald Graham on quasirandom graphs and quasirandom sets, and the results of Timothy Gowers on quasirandom groups. To further display the connection between randomness and structuredness, we will also present some other influential results on the subject, i. e. Roth's Theorem on arithmetical progression on subsets of Zn, Erdős' Theorem on sum-free sets of integers, and the Alon-Boppana Bound for the spectral expansion of a graph.