  Quantum technologies are enjoying an unprecedented popularity, and some
applications are already in the market. This thesis studies two phenomena that
are behind a lot of quantum technologies: entanglement and nonlocality. We
focus on multipartite systems, and ask what configurations of those systems are
more useful than others. 'Usefulness' takes on different meanings depending on
the context, but, roughly speaking, we aim for more entanglement or more
nonlocality. Chapter 2 develops a resource theory of entanglement with a unique
multipartite maximally entangled state. Chapter 3 shows that any connected
network of bipartite pure entangled states is genuine multipartite nonlocal
(GMNL). Chapter 4 shows that, unlike in the case of pure states, topology is
crucial to determine whether networks of bipartite mixed entangled states are
genuine multipartite entangled. We also obtain, to our knowledge, the first
example of superactivation of GMNL. In a departure from the main ideas explored
in previous chapters, Chapter 5 is devoted to developing a physical principle
inspired by a seminal result in epistemics. We contend that the principle must
hold for any theory of Nature and intend for it to rule out post-quantum
theories which are consistent with experimentally observed results.
