As the introductory talk in the "Seeing the network for the trees: Methodological and empirical advances in reticulate evolution" symposium, we will cover the overview of phylogenetic networks, specifically, we will focus on the definition of phylogenetic networks, different classes of phylogenetic networks as well as most widely used inference methods to infer phylogenetic networks from a variety of datatypes. We will conclude with an overview of the state-of-the-art of network inference research as well as the main limitations of these methods.