The Formation and Evolution of Thorne-Zytkow Objects

I will first review the various channels that can lead to the formation of Thorne-Zytkow objects (TZOs) and discuss the physical uncertainties and recent theoretical developments regarding the formation process, the modeling of TZOs themselves and their expected lifetimes. I will then outline nucleosynthesis signatures by which different types of TZOs can be distinguished observationally and relate this to recent observational studies. Finally, I will discuss their final fate and speculations on how their final evolution might be related to unusual supernovae (including superluminous supernovae) and black-hole binaries.