  Matching, capturing allocation of items to unit-demand buyers, or tasks to
workers, or pairs of collaborators, is a central problem in economics. Indeed,
the growing prevalence of matching-based markets, many of which online in
nature, has motivated much research in economics, operations research, computer
science, and their intersection. This brief survey is meant as an introduction
to the area of online matching, with an emphasis on recent trends, both
technical and conceptual.
