  In this thesis we investigate some aspects of quantum field theories from a
holographic perspective. In the first chapters we examine in detail a
one-paremeter family of three-dimensional gauge theories by means of their type
IIA gravity duals. We analyse features such as their confinement nature,
spectrum, entanglement properties or thermal phase transitions. This family
interpolates between quasi-conformal and quasi-confining physics. In the last
two chapters, we use bottom-up models to study complex conformal field theories
and transport properties of dense QCD respectively.
