The d-dimensional Gaussian free field (GFF), also called the (Euclidean
bosonic) massless free field, is a d-dimensional-time analog of Brownian
motion. Just as Brownian motion is the limit of the simple random walk (when
time and space are appropriately scaled), the GFF is the limit of many
incrementally varying random functions on d-dimensional grids. We present an
overview of the GFF and some of the properties that are useful in light of
recent connections between the GFF and the Schramm-Loewner evolution.