  Stars do not generally form in isolation. Instead, they form in clusters, and
in these clustered environments newborn stars can have profound effects on one
another and on their parent gas clouds. Feedback from clustered stars is almost
certainly responsible for a number of otherwise puzzling facts about star
formation: that it is an inefficient process that proceeds slowly when averaged
over galactic scales; that most stars disperse from their birth sites and
dissolve into the galactic field over timescales $\ll 1$ Gyr; and that newborn
stars follow an initial mass function (IMF) with a distinct peak in the range
$0.1 - 1$ $M_\odot$, rather than an IMF dominated by brown dwarfs. In this
review we summarize current observational constraints and theoretical models
for the complex interplay between clustered star formation and feedback.
