There will be 3 lectures: - The first is devoted to explaining the main concepts and we will take the opportunity to talk about other statistical properties of dynamical systems, such as Central Limit Theorems, Laws of large numbers or Birkhoff's ergodic theorem, Poincaré's recurrence theorem and Kac's theorem. - In the second we will give the connection between EVL and HTS/RTS in the absence of clustering. - In the third we will address the presence of clustering and its connection with periodicity.