What is World History?
Put simply, world history is macrohistory. It is transregional, transnational, and transcultural.
Although it is important for students of world history to have a deep and nuanced understanding of each of the various cultures, states, and other entities that have been part of the vast mosaic of human history, the world historian stands back from these individual elements in that mosaic to take in the entire picture, or at least a large part of that picture. Consequently, the world historian studies phenomena that transcend single states, regions, and cultures, such as cultural contact and exchange and movements that have had a global or at least a transregional impact. The world historian also often engages in comparative history, and in that respect might be thought of as a historical anthropologist.
World history is not, therefore, the study of the histories of discrete cultures and states one after another and in isolation from one another. It is also not necessarily global history. That is, world history is not simply the study of globalization after 1492.
As long as one focuses on the big picture of cultural interchange and/or comparative history, one is a practicing world historian. Therefore, for example, a number of noted world historians focus on travel and cultural exchange within the vast premodern Islamic World. Others study the exchange of goods, ideas, flora, and fauna across the so-called Silk Road that criss-crossed Eurasia from roughly 200 BCE to about 1350 CE. Others concentrate on comparative holy wars both within and outside of the Abrahamic religions of Judaism Christianity, and Islam. Still others have chosen to study in depth the global or transregional impact of single items or classes of items, such as the development and use of fire arms across the world from antiquity to the present or the significant roles that such apparently humble items as cotton and codfish have played across the vast span of human history. Given the current pandemic of AIDS and the ever-present fear of new pandemics, the role of disease in human history has also become an important and timely topic of study and teaching.