Organolead halide perovskites have attracted a lot of attention over the recent years mostly due to their bright prospective application in photovoltaic devices. For further development, characterization of their physical properties plays a seminal role in order to gain an in-depth understanding of these mid-bandgap ionic semiconductors. Their unique optical and electronic properties are a result of their characteristic electronic structure. Temperature dependent optical spectroscopy, i.e., absorption and photoluminescence (PL) characterization, gives access to their electronic nature that draws strong correlations to their structural properties. Those properties include static and dynamic disorder, and defects or phase transitions, which will be demonstrated in the first part of this research view. The second part focuses on ion migration in these hybrid semiconductors, which can strongly affect the slow dynamics of optical properties. Light-activated ions result in a number of complex processes that can lead to an increase, but also a decrease of PL intensity, or induce PL intermittency. Parameters like light intensity, crystal quality, and defect density all influence these processes, and ultimately the electronic nature of the hybrid perovskites. We will briefly summarize current achievements and point out challenges for upcoming research.