The definition of virtual fixtures by Rosenberg is much broader than simply providing guidance of the end-effector. For example, auditory virtual fixtures are used to increase the user awareness by providing audio clues that helps the user by providing multi modal cues for localization of the end-effector. Rosenberg argues that the success of virtual fixtures is not only because the user is guided by the fixture, but that the user experiences a greater presence and better localization in the remote workspace. However, in the context of human-machine collaborative systems, the term virtual fixtures is often used to refer to a task dependent virtual aid that is overlaid upon a real environment and guides the user's motion along desired directions while preventing motion in undesired directions or regions of the workspace. This is the type of virtual fixtures that is described in detail in the next section of this article.