The rare earth magnetic pyrochlore oxides, of formula R2M2O7, have attracted much attention over the past twenty years because of the plethora of interesting thermodynamic and magnetic phenomena that they display . In R2M2O7, R is a trivalent rare earth ion (R=Gd,Tb,Dy,Ho,Er,Yb) and M is a tetravalent transition metal ion (M=Ti,Sn,Zr,Hf). Among these materials, the (Ho,Dy)2(Ti,Sn)2O7, called "spin ice" because they exhibit a low-temperature state with extensive magnetic entropy and are closely related to the problem of proton disorder in water ice, have been the most systematically investigated. In this talk I will review some of the phenomenologies and point out where the community currently stands in terms of their theoretical understanding.
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