Internet Studies is an interdisciplinary and multidisciplinary field of fundamental and applied research that integrates different research disciplines with a common object, that is, the Internet. This review article gives a definition and a brief description of the structure of Internet Studies as part of the social sciences, and introduces the research agenda of this field, including the most cutting-edge research issues. The agenda of Internet Studies is related to classical sociological issues such as inequality, online communities, and social capital, as well as topics related to the study of transformations in different spheres of society such as politics, public health and medicine, and education, which is analyzed in more detail. Two main theoretical approaches, the network society theory and critical theory of the Internet and society within which the influence of the Internet on society is interpreted, are briefly described. We conclude that the present directions of Internet research often intersect with each other, and that the perspective of a more complete study of the mechanisms that mediate social changes related to the Internet connecting online and offline sociality into a single space opens at these intersections.