  Not all the light in galaxy groups and clusters comes from stars that are
bound to galaxies. A significant fraction of it constitutes the so-called
intracluster or diffuse light (ICL), a low surface brightness component of
groups/clusters generally found in the surroundings of the brightest cluster
galaxies and intermediate/massive satellites. In this review, I will describe
the mechanisms responsible for its formation and evolution, considering the
large contribution given to the topic in the last decades by both the
theoretical and observational sides. Starting from the methods that are
commonly used to isolate the ICL, I will address the remarkable problem given
by its own definition, which still makes the comparisons among different
studies not trivial, to conclude by giving an overview of the most recent works
that take advantage of the ICL as a luminous tracer of the dark matter
distribution in galaxy groups and clusters.
