Abstract
This thesis investigates models of dark energy based on generalized theories in the framework of the teleparallel equivalent of general relativity. We study the cosmic background evolution in the quintessence-inspired teleparallel dark energy model. We explore the cosmological perturbation of $f(T)$ gravity, and we analyze the similar perturbation scenario of teleparallel quintessence model. We check the viability of teleparallel dark energy theories in the weak-field regime through the parametrized post-Newtonian approach, and finally, we show that the Cauchy problem in the generalized teleparallel theory can be resolved by a time-gauge fixing condition.