In order to fully understand the usefulness of the AVP, it can be fruitful to first have a look at how the large-scale structures in the Universe have formed, then from a theoretical viewpoint. But before that, let us have a quick glance at what sort of structures the Universe actually consists of, in Section 2.1. Then, in Section 2.2, a presentation of some of the more popular theories of how structures came into being will be given, both linear and non-linear, including a short historical review. Section 2.3 will deal with the linear theory for velocity fields, and the chapter is being closed in Section 2.4 by taking a closer look at our neighbourhood in the Universe; the Local Group and the Local Neighbourhood.