Despite its importance to the VO, a registry‛s destiny is to go largely unnoticed by most users, providing its services to other applications behind the scenes. Consequently, most who come to the VO as consumers do not need to understand most of the concepts presented in this chapter. Users that wish to employ advanced discovery techniques will benefit from a deeper understanding of the registry metadata model. Publishers — those who make data or services available to others through the VO — will also benefit from this closer look; not only will they see the role of registries in the publication process, they will better understand the importance of providing good descriptions of their assets so that users can make the most of them.