From Instagram, Gojek and Uber to Alibaba, Amazon Web Services and ChatGPT, platforms shape nearly every aspect of modern life. They influence how we communicate, work, learn, shop, vote, and connect. But what exactly are platforms? How do they operate and how did they become so powerful?Platforms offers a clear and critical introduction to platforms and platformisation, and to the burgeoning field of platform studies. Written by leading experts in the field, the book explains how platforms operate as companies, services, and technologies or infrastructures, and how they shape economies, cultures, and institutions around the world. Drawing on real-world examples, Anne Helmond and Fernando van der Vlist unpack key concepts such as platform power, governance, and strategy. They show how platforms generate value, influence public life, and create new forms of dependency and control. The book also introduces practical approaches for analysing platforms, ranging from examining financial filings and policy documents to conducting interface walkthroughs and studying technical artefacts. Accessible, timely, and grounded in global perspectives, this book is a must-read for students and scholars across the social sciences and humanities, as well as policymakers and anyone seeking to understand how platforms shape our world and how we might study them critically.