In this thesis, several theoretical concepts relating to the large-scale structure of the universe are presented. In particular, various aspects of the hierarchical scenario are investigated. The initial perturbation field and its early evolution are discussed in Chapter 3. Chapter 4 is concerned with two-point correlation functions for galaxies, clusters and super-clusters. In Chapter 5, some effects of using velocity as a distance measure are examined. In particular, it will be argued that caustics in redshift space are an almost inevitable feature of the hierarchical scenario. Chapter 6 concentrates on the possibity that quasar Ly-α absorption lines are redshift caustics.