  We review recent work in which compactifications of string and M theory are
constructed in which all scalar fields (moduli) are massive, and supersymmetry
is broken with a small positive cosmological constant, features needed to
reproduce real world physics. We explain how this work implies that there is a
``landscape'' of string/M theory vacua, perhaps containing many candidates for
describing real world physics, and present the arguments for and against this
idea. We discuss statistical surveys of the landscape, and the prospects for
testable consequences of this picture, such as observable effects of moduli,
constraints on early cosmology, and predictions for the scale of supersymmetry
breaking.
