The effects of climate change, whether they be via slow- or rapid-onset events such as extreme events, are inflicting devastating losses and damage on communities around the world, with the most vulnerable affected the most. Although the negative impacts of climate change and the concept of loss and damage are included in international conventions, such as the United Nations Warsaw International Mechanism for Loss and Damage and Article 8 of the Paris Agreement, these stop short of providing clear compensation mechanisms. The science of loss and damage has evolved with the development of extreme event attribution science, which assesses the probability of an extreme event being influenced by anthropogenic greenhouse gas emissions, but loss and damage still suffers from the lack of a clear definition and measurability and is further complicated by debates on climate justice and shared but differentiated responsibilities. This primer presents an overview of loss and damage, discusses the complexities and knowledge gaps, and proposes next steps for an interdisciplinary research agenda.