In recent years Augmented Reality (AR) has become more and more popular, especially since the availability of mobile devices, such as smartphones or tablets, brought AR into our everyday life. Although the AR community has not yet agreed on a formal definition of AR, some work focused on proposing classifications of existing AR methods or applications. Such applications cover a wide variety of technologies, devices and goals, consequently existing taxonomies rely on multiple classification criteria that try to take into account AR applications diversity. In this paper we review existing taxonomies of augmented reality applications and we propose our own, which is based on (1) the number of degrees of freedom required by the tracking of the application, as well as on (2) the visualization mode used, (3) the temporal base of the displayed content and (4) the rendering modalities used in the application. Our taxonomy covers location-based services as well as more traditional vision-based AR applications. Although AR is mainly based on the visual sense, other rendering modalities are also covered by the same degree-of-freedom criterion in our classification.