This chapter explains the contradictory observations that have been made on LaAlO3/ Strontium Titanate (SrTiO3) heterostructures, and closely related systems, which have been investigated extensively, as well as explored theoretically. It reviews the experimental evidence for magnetic phenomena at the LaAlO3/SrTiO3 interface. The chapter argues that essentially all of the signatures of magnetism can be sorted into two distinct categories: magnetic phases involving local magnetic moments and their coupling to itinerant electrons and metamagnetic effects that are mediated by attractive electron-electron interactions that do not involve local moments. It also reviews possible candidates for the local moments that give rise to the ferromagnetic phases and focus on arguments for one potential source: oxygen vacancies. Theories of magnetism at the LaAlO3/SrTiO3 interface usually begin with a theory of the ferromagnetic phase. With the discovery of localized ferromagnetic patches separated by a paramagnetic phase, additional detail was necessary.