First hypotheses about brain networks emerged in 19th century with Ramón y Cajal's "neuron doctrine". He believed that connections between neurons are governed by laws of conservation for time, space and material. Much of the evidence for this hypotheses accumulated in the last 25 years, when whole brain imaging of living human brain has become feasible and widespread.
In the talk Andraž compared brain networks to transportation networks. First, the difference between structural and functional networks can be compared to the difference between roads (anatomical connections between brain regions) and traffic (information flow).
Second, while brain and transportation networks seem completely different on the surface their organization is guided by same principles. On the one hand, nodes (brain regions or neurons, depending on the level of observation) connect to other nodes in spatial proximity and form modules (communities), thus preserving space and material. On the other hand, these spatially distant modules are connected through smaller number of hubs. Communication between modules flows through small number of long range connections. In this way, information still travels fast between modules. Similarly, there are no direct flight connections between Ljubljana and some random town in USA, but these locations are nevertheless connected via hubs. To travel from Ljubljana to USA, one must travel via Frankfurt, Heathrow or some other important airport.
At the end, Andraž talked about clinical utility of brain networks. As an example he presented the study by Drysdale et al. (2017; https://doi.org/10.1038/nm.4246). In this study resting state functional brain networks were used to find new diagnostic categories (biotypes) of depression which were defined both in terms of symptoms and connectivity. These diagnostic categories were then used to predict response to TMS treatment. While the study hasn't been replicated (Dinga et al., 2019; https://doi.org/10.1016/j.nicl.2019.101796), it can be viewed as a concept of how brain imaging can improve our definitions and treatment of brain disorders.