The purpose of this narrative is to describe and explain the function of learning centers in American colleges and universities. Since the early 1960's nearly every four-year institution has created or increased support for some kind of learning center with the ostensible aim of improving the academic performance of its enrolled students. In spite of the increased visibility of learning centers in higher education, however, accounts of them in the educational literature have been written in excessively abstract language, rendering them conceptually vague and fragmented. This narrative will present a view of learning centers that identifies, describes and elaborates their functions in clear concrete terms, to wit, it will: 1) identify characteristics that distinguish LCs from current and historically competing student academic support services; 2) specify several properties that link today's learning centers conceptually; 3) describe the work in done in LCs, i.e. what are its goals and the acceptable means of achieving them; and 4) recommend current learning practices that need improving. It will, in short, address the question what is a learning center?