Graphs are everywhere around us. Your social network is a graph of people and relations. So is your family. The roads you take to go from point A to point B constitute a graph. The links that connect this webpage to others form a graph. When your employer pays you, your payment goes through a graph of financial institutions.
Basically, anything that is composed of linked entities can be represented as a graph. Graphs are excellent tools to visualize relations between people, objects, and concepts. Beyond visualizing information, however, graphs can also be good sources of data to train machine learning models for complicated tasks.
Graph neural networks (GNN) are a type of machine learning algorithm that can extract important information from graphs and make useful predictions. With graphs becoming more pervasive and richer with information, and artificial neural networks becoming more popular and capable, GNNs have become a powerful tool for many important applications.