In this thesis we focus on the study of strongly interacting systems using the gauge/gravity duality. We begin by providing an overview of the history of string theory and we briefly describe the basic properties of QCD and the N = 4 super Yang-Mills. There are some warm up chapters, where we build our understanding on the basic facets of the AdS/CFT, namely field dynamics in AdS and some basic statements about conformal field theories. After that, we describe how it is possible to introduce fundamental degrees of freedom in the context of the AdS/CFT duality and we motivate the bottom-up holographic approach. We are using all probe-brane setups in the type IIA and type IIB theories that preserve eight supercharges in order to study the dynamics and mass spectra of spin- 1/2 fields. We are allowing for higher dimensional interactions and we examine their effect on the spectrum. Using this knowledge, which stems from the formal top-down constructions, we proceed to use Dynamic AdS/Yang-Mills in order to obtain holographic predictions for models in which the Higgs is a composite state. We end this thesis by providing our proposals for future work.