Two-dimensional (2D) halide perovskites (HPs) are self-assembled multi-quantum wells with excitonic peculiarities. They afford favorable moisture and photothermal stability compared to traditional 3D counterparts. However, the energy conversion properties of 2D HPs are highly site-distinct, and they are found to have complicated origins that are associated with diverse local exciton relaxation dynamics, hence causing researchers severe bewilderment when targeting customized applications. This Review intends to offer a thorough survey on this topic. We first introduce the crystallographic structures of 2D HPs and how they render a quantum-well electronic structure. Subsequently, we elaborate on the exciton transport mechanisms in 2D HPs to interpret how excitons arrive at various local sites. Then we concretely introduce the diversiform local/bulk exciton relaxation dynamics that give rise to the wealthy energy conversion attributes. Finally, challenges and opportunities for better understanding and manipulating the exciton dynamics of this promising class of materials are discussed.