The Physics of the Solar Wind Termination Shock: What are the Ingredients?

After a 27 year journey, Voyager 1 crossed the solar wind termination shock, the first boundary separating the solar system from the rest of the galaxy. Voyager's \textit{in situ} observations both before and after the shock crossing presented some surprises, and only some of these have so far been explained. In this talk, we discuss some of these observations and some of the physical effects (magnetic fields, charge exchange, etc.) that must be included in MHD modeling of the solar wind termination and the global heliosphere in order to understand the observations. Previous models and observations of the termination shock and global heliosphere will also be discussed.