We review many of the basic properties of star cluster systems , and focus in particular on how they relate to their host galaxy properties and ambient environment .
The cluster mass and luminosity functions are well approximated by power-laws of the form Ndm \propto M ^ { \alpha } dm , with \alpha \sim - 2 over most of the observable range .
However , there is now clear evidence that both become steeper at high masses/luminosities , with the value of the downward turn dependent on environment .
The host galaxy properties also appear to affect the cluster formation efficiency ( \Gamma - i.e. , the fraction of stars that form in bound clusters ) , with higher star-formation rate density galaxies having higher \Gamma values .
Within individual galaxies , there is evidence for \Gamma to vary by a factor of 3 - 4 , likely following the molecular gas surface density , in agreement with recent predictions .
Finally , we discuss cluster disruption and its effect on the observed properties of a population , focussing on the age distribution of clusters .
We briefly discuss the expectations of theoretical and numerical studies , and also the observed distributions in a number of galaxies .
Most observational studies now find agreement with theoretical expectations , namely nearly a constant cluster age distribution for ages up to \sim 100 Myr ( i.e .
little disruption ) , and a drastic steepening above this value caused by a combination of cluster disruption and incompleteness .
Rapid cluster disruption for clusters with ages < 100 Myr is ruled out for most galaxies .